TS-2361: improve regex_remap plugin loading semantics

The location of the regex_remap configuration is not well-defined
if it is a relative path. Either it will be found in the current
directory (which is undefined), or a hard-coded global directory
will be used.

This change always uses the absolute path if an absolute path is
provided. If a relative path is provided, then we load that relative
to the configured Traffic Server configuration directory.
TS-2360 Fix usage of TSMimeHdrFieldValueStringGet() in some plugins.

This also adds Sphinx docs for the TSMimeHdrFieldValueStringGet() and
family of APIs. Finally, it also adds a regression test for the -1
IDX argument.
Added TS-2360.
TS-2360 Improve the example slightly, but it is still an example
TS-2364: Introduce slice notation to field syntax in log format

Now, we have two kind of field syntax in log format:
(1) simple syntax: '%<field>', for example: %<cqu>
(2) container field, syntax: '%<{field}container>',
    for example: %<{Referer}cqh>.

This patch introduces slice notation to field syntax, so that we can easy to
limit the length of filed's output. With slice notation, the filed syntax will
looks like:
(1) '%<field[start:end]>'
(2) '%<{field}container[start:end]>'

In both forms, slice notation can be omitted, which means the whole field.

But with one limitation: slice notation makes sense only when the field is
string type and it shouldn't be ip/timestamp which are converted to
string from integer.

We can see the syntax of slice notation from Python, Golang, it's pretty
simple:
  [start:end] //items start through end-1
  [start:]    //items start through the rest of the array
  [:end]      //items from the beginning through end-1
  [:]         //the whole array(by default)

For example,
  '%<cqup>'       //the whole characters of <cqup>.
  '%<cqup>[:]'    //the whole characters of <cqup>.
  '%<cqup[0:30]>' //the first 30 characters of <cqup>.
  '%<cqup[-10:]>' //the last 10 characters of <cqup>.
  '%<cqup[:-5]>'  //everything except the last 5 characters of <cqup>.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
TS-2352: refine THREAD_ALLOC feature

1) Move the definition of "ProxyAllocator xxxx" in EThread class to its
   parent Thread class, so that all threads can feel free to use
   THREAD_ALLOC feature.

2) Disable THREAD_ALLOC when enable reclaimable-freelist as reclaimable
   freelist has implemented thread-local pool.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
set the tracker_event to NULL if we cancelled the event.
fix linking traffic_api_cli_remote on ubuntu
Add a new field: '%<chp>', "client_host_port" to LogFormat

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
TS-1468: Check vary and accept headers on non-200 responses in cache
TS-2327: TSRedirectUrlSet does not perform DNS lookup of redirected OS
TS-2374: abort the producer to avoid httpsm hung if none of it`s
consumer is alive.
Add CHANGES for TS-2379
TS-2360: Update TSMimeHdrFieldValueStringGet docs
convert CRLF->LF, make sure it never happens again

we add a git attributes to make sure that text files are stored
git-internally as LF. This way we avoid conflicts betweent Unix and
Windows (yes, some of our developers sometimes use Windows).

Additionally, I remove the executable flag from files that don't need to
be executed.