CLEANUP: regex: Create regex_comp function that compiles regex using compilation options

The current file "regex.h" define an abstraction for the regex. It
provides the same struct name and the same "regexec" function for the
3 regex types supported: standard libc, basic pcre and jit pcre.

The regex compilation function is not provided by this file. If the
developper wants to use regex, he must write regex compilation code
containing "#define *JIT*".

This patch provides a unique regex compilation function according to
the compilation options.

In addition, the "regex.h" file checks the presence of the "#define
PCRE_CONFIG_JIT" when "USE_PCRE_JIT" is enabled. If this flag is not
present, the pcre lib doesn't support JIT and "#error" is emitted.
BUG/MEDIUM: http: accept full buffers on smp_prefetch_http

Bertrand Jacquin reported a but when using tcp_request content rules
on large POST HTTP requests. The issue is that smp_prefetch_http()
first tries to validate an input buffer, but only if the buffer is
not full. This test is wrong since it must only be performed after
the parsing has failed, otherwise we don't accept POST requests which
fill the buffer as valid HTTP requests.

This bug is 1.5-specific, no backport needed.
BUG/MINOR: acl: implicit arguments of ACL keywords were not properly resolved

William Lallemand reported a bug which happens when an ACL keyword using an
implicit argument (eg: a proxy name) is used : the keyword is not properly
set in the arglist field, resulting in an error about the previous keyword
being returned, or "(null)" if the faulty ACL appears first.

The bug only affects error reporting and is 1.5-specific, so no backport is
nedeed.
MINOR: Makefile: provide cscope rule

"make cscope" builds tags for cscope.
CLEANUP: The function "regex_exec" needs the string length but in many case they expect null terminated char.

If haproxy is compiled with the USE_PCRE_JIT option, the length of the
string is used. If it is compiled without this option the function doesn't
use the length and expects a null terminated string.

The prototype of the function is ambiguous, and depends on the
compilation option. The developer can think that the length is always
used, and many bugs can be created.

This patch makes sure that the length is used. The regex_exec function
adds the final '\0' if it is needed.
MINOR: http: some exported functions were not in the header file

Export the following functions:
 - find_hdr_value_end
 - http_header_match2
 - http_remove_header2
 - http_header_add_tail2
MINOR: http: change url_decode to return the size of the decoded string.

Currently url_decode returns 1 or 0 depending on whether it could decode
the string or not. For some future use cases, it will be needed to get the
decoded string length after a successful decoding, so let's make it return
that value, and fall back to a negative one in case of error.
BUILD/MINOR: missing header file

In the header file "types/proto_http.h", the list are used
but the header file "mini-clist.h" is not included.
BUG/MEDIUM: session: risk of crash on out of memory conditions

In session_accept(), if we face a memory allocation error, we try to
emit an HTTP 500 error message in HTTP mode. The problem is that we
must not use http_error_message() for this since it dereferences the
session which can be NULL in this case.

We don't need the session to build the error message anyway since
this function only uses it to retrieve the backend and frontend to
get the most suited error message. Let's pick it ourselves, we're
at the beginning of the session, only the frontend is relevant.

This bug is 1.5-specific.
BUG/MINOR: peers: set the accept date in outgoing connections

Without this, "show sess" on the CLI reports a wrong age.
BUG/MEDIUM: tcp: do not skip tracking rules on second pass

The track-sc* tcp rules are bogus. The test to verify if the
tracked counter was already assigned is performed in the same
condition as the test for the action. The effect is that a
rule which tracks a counter that is already being tracked
is implicitly converted to an accept because the default
rule is an accept.

This bug only affects 1.5-dev releases.