MINOR: tools: add new functions to quote-encode strings

qstr() and cstr() will be used to quote-encode strings. The first one
does it unconditionally. The second one is aimed at CSV files where the
quote-encoding is only needed when the field contains a quote or a comma.
DOC: clarify the CSV format

Indicate that the text cells in the CSV format may contain quotes to
escape ambiguous texts. We don't have this case right now since we limit
the output, but it may happen in the future.
MEDIUM: stats: report the last check and last agent's output on the CSV status

Now that we can quote unsafe string, it becomes possible to dump the health
check responses on the CSV page as well. The two new fields are "last_chk"
and "last_agt".
MINOR: freq_ctr: introduce a new averaging method

While the current functions report average event counts per period, we are
also interested in average values per event. For this we use a different
method. The principle is to rely on a long tail which sums the new value
with a fraction of the previous value, resulting in a sliding window of
infinite length depending on the precision we're interested in.

The idea is that we always keep (N-1)/N of the sum and add the new sampled
value. The sum over N values can be computed with a simple program for a
constant value 1 at each iteration :

    N
  ,---
   \       N - 1              e - 1
    >  ( --------- )^x ~= N * -----
   /         N                  e
  '---
  x = 1

Note: I'm not sure how to demonstrate this but at least this is easily
verified with a simple program, the sum equals N * 0.632120 for any N
moderately large (tens to hundreds).

Inserting a constant sample value V here simply results in :

   sum = V * N * (e - 1) / e

But we don't want to integrate over a small period, but infinitely. Let's
cut the infinity in P periods of N values. Each period M is exactly the same
as period M-1 with a factor of ((N-1)/N)^N applied. A test shows that given a
large N :

     N - 1           1
  ( ------- )^N ~=  ---
       N             e

Our sum is now a sum of each factor times  :

   N*P                                     P
  ,---                                   ,---
   \         N - 1               e - 1    \     1
    >  v ( --------- )^x ~= VN * -----  *  >   ---
   /           N                   e      /    e^x
  '---                                   '---
  x = 1                                  x = 0

For P "large enough", in tests we get this :

    P
  ,---
   \     1        e
    >   --- ~=  -----
   /    e^x     e - 1
  '---
  x = 0

This simplifies the sum above :

   N*P
  ,---
   \         N - 1
    >  v ( --------- )^x = VN
   /           N
  '---
  x = 1

So basically by summing values and applying the last result an (N-1)/N factor
we just get N times the values over the long term, so we can recover the
constant value V by dividing by N.

A value added at the entry of the sliding window of N values will thus be
reduced to 1/e or 36.7% after N terms have been added. After a second batch,
it will only be 1/e^2, or 13.5%, and so on. So practically speaking, each
old period of N values represents only a quickly fading ratio of the global
sum :

  period    ratio
    1       36.7%
    2       13.5%
    3       4.98%
    4       1.83%
    5       0.67%
    6       0.25%
    7       0.09%
    8       0.033%
    9       0.012%
   10       0.0045%

So after 10N samples, the initial value has already faded out by a factor of
22026, which is quite fast. If the sliding window is 1024 samples wide, it
means that a sample will only count for 1/22k of its initial value after 10k
samples went after it, which results in half of the value it would represent
using an arithmetic mean. The benefit of this method is that it's very cheap
in terms of computations when N is a power of two. This is very well suited
to record response times as large values will fade out faster than with an
arithmetic mean and will depend on sample count and not time.

Demonstrating all the above assumptions with maths instead of a program is
left as an exercise for the reader.
MEDIUM: session: maintain per-backend and per-server time statistics

Using the last rate counters, we now compute the queue, connect, response
and total times per server and per backend with a 95% accuracy over the last
1024 samples. The operation is cheap so we don't need to condition it.
MEDIUM: stats: report per-backend and per-server time stats in HTML and CSV outputs

The time statistics computed by previous patches are now reported in the
HTML stats in the tips related to the total sessions for backend and servers,
and as separate columns for the CSV stats.
MEDIUM: http: add actions "replace-header" and "replace-values" in http-req/resp

This patch adds two new actions to http-request and http-response rulesets :
  - replace-header : replace a whole header line, suited for headers
                     which might contain commas
  - replace-value  : replace a single header value, suited for headers
                     defined as lists.

The match consists in a regex, and the replacement string takes a log-format
and supports back-references.
BUG/MINOR: http: fix typos in previous patch

When I renamed the modify-header action to replace-value, one of them
was mistakenly set to "replace-val" instead. Additionally, differentiation
of the two actions must be done on args[0][8] and not *args[8]. Thanks
Thierry for spotting...
MINOR: regex: Create JIT compatible function that return match strings

This patchs rename the "regex_exec" to "regex_exec2". It add a new
"regex_exec", "regex_exec_match" and "regex_exec_match2" function. This
function can match regex and return array containing matching parts.
Otherwise, this function use the compiled method (JIT or PCRE or POSIX).

JIT require a subject with length. PCREPOSIX and native POSIX regex
require a null terminted subject. The regex_exec* function are splited
in two version. The first version take a null terminated string, but it
execute strlen() on the subject if it is compiled with JIT. The second
version (terminated by "2") take the subject and the length. This
version adds a null character in the subject if it is compiled with
PCREPOSIX or native POSIX functions.

The documentation of posix regex and pcreposix says that the function
returns 0 if the string matche otherwise it returns REG_NOMATCH. The
REG_NOMATCH macro take the value 1 with posix regex and the value 17
with the pcreposix. The documentaion of the native pcre API (used with
JIT) returns a negative number if no match, otherwise, it returns 0 or a
positive number.

This patch fix also the return codes of the regex_exec* functions. Now,
these function returns true if the string match, otherwise it returns
false.
MEDIUM: regex: replace all standard regex function by own functions

This patch remove all references of standard regex in haproxy. The last
remaining references are only in the regex.[ch] files.

In the file src/checks.c, the original function uses a "pmatch" array.
In fact this array is unused. This patch remove it.
MEDIUM: regex: Remove null terminated strings.

The new regex function can use string and length. The HAproxy buffer are
not null-terminated, and the use of the regex_exec* functions implies
the add of this null character. This patch replace these function by the
functions which takes a string and length as input.

Just the file "proto_http.c" is change because this one is more executed
than other. The file "checks.c" have a very low usage, and it is not
interesting to change it. Furthermore, the buffer used by "checks.c" are
null-terminated.
MINOR: regex: Use native PCRE API.

The pcreposix layer (in the pcre projetc) execute strlen to find
thlength of the string. When we are using the function "regex_exex*2",
the length is used to add a final \0, when pcreposix is executed a
strlen is executed to compute the length.

If we are using a native PCRE api, the length is provided as an
argument, and these operations disappear.

This is useful because PCRE regex are more used than POSIC regex.
MEDIUM: ssl: ignored file names ending as '.issuer' or '.ocsp'.

We don't want to load these files found in directories specified in "crt" or
"crt-list".

These suffixes are reserved for OCSP stapling.
MEDIUM: ssl: basic OCSP stapling support.

The support is all based on static responses. This doesn't add any
request / response logic to HAProxy, but allows a way to update
information through the socket interface.

Currently certificates specified using "crt" or "crt-list" on "bind" lines
are loaded as PEM files.
For each PEM file, haproxy checks for the presence of file at the same path
suffixed by ".ocsp". If such file is found, support for the TLS Certificate
Status Request extension (also known as "OCSP stapling") is automatically
enabled. The content of this file is optional. If not empty, it must contain
a valid OCSP Response in DER format. In order to be valid an OCSP Response
must comply with the following rules: it has to indicate a good status,
it has to be a single response for the certificate of the PEM file, and it
has to be valid at the moment of addition. If these rules are not respected
the OCSP Response is ignored and a warning is emitted. In order to  identify
which certificate an OCSP Response applies to, the issuer's certificate is
necessary. If the issuer's certificate is not found in the PEM file, it will
be loaded from a file at the same path as the PEM file suffixed by ".issuer"
if it exists otherwise it will fail with an error.

It is possible to update an OCSP Response from the unix socket using:

  set ssl ocsp-response <response>

This command is used to update an OCSP Response for a certificate (see "crt"
on "bind" lines). Same controls are performed as during the initial loading of
the response. The <response> must be passed as a base64 encoded string of the
DER encoded response from the OCSP server.

Example:
  openssl ocsp -issuer issuer.pem -cert server.pem \
               -host ocsp.issuer.com:80 -respout resp.der
  echo "set ssl ocsp-response $(base64 -w 10000 resp.der)" | \
               socat stdio /var/run/haproxy.stat

This feature is automatically enabled on openssl 0.9.8h and above.

This work was performed jointly by Dirkjan Bussink of GitHub and
Emeric Brun of HAProxy Technologies.
MINOR: missing regex.h include
MINOR: ssl/cli: Fix unapropriate comment in code on 'set ssl ocsp-response'
MEDIUM: ssl: add 300s supported time skew on OCSP response update.

OCSP_MAX_RESPONSE_TIME_SKEW can be set to a different value at
compilation (default is 300 seconds).
DOC: remove the ultra-obsolete TODO file

This one was still written in french and outdated since 1.4 or so.
DOC: update roadmap

1.5-dev is closed, it will not get any more updates.
DOC: minor updates to the README

- mention that this is a stable version
- stop mentionning the outdated contrib.html page.