Upgrade xdiff to version used in core git 2.4.5 (0df0541).
Corrects an issue where an LF is added at EOF while applying
an unrelated change (ba31180), cleans up some unused code (be89977 and
e5b0662), and provides an improved callback to avoid leaking internal
(to xdiff) structures (467d348).
This also adds some additional functionality that we do not yet take
advantage of, namely the ability to ignore changes whose lines are
all blank (36617af).
Versions prior to 0.9.8f did not have this function, rhel/centos5 are still on a
heavily backported version of 0.9.8e and theoretically supported until March 2017
Without this ifdef, I get the following link failure:
```
CMakeFiles/libgit2_clar.dir/src/openssl_stream.c.o: In function `openssl_connect':
openssl_stream.c:(.text+0x45a): undefined reference to `SSL_set_tlsext_host_name'
collect2: error: ld returned 1 exit status
make[6]: *** [libgit2_clar] Error 1
```
Introduce `git__getenv` which is a UTF-8 aware `getenv` everywhere.
Make `cl_getenv` use this to keep consistent memory handling around
return values (free everywhere, as opposed to only some platforms).
Don't use the filter's free callback to free the actual data structure
holding the filter, as we may not always actually initialize it (the
test may be skipped).
The regex we use to look at the gitmodules file does not correctly
delimit the name of submodule which we want to look up and puts '.*'
straight after the name, maching on any submodule which has the seeked
submodule as a prefix of its name.
Add the missing '\.' in the regex so we want a full stop to exist both
before and after the submodule name.
The function was removed, but its declaration and changelog entry about
its removal were forgotten.
The comment in the test doesn't make any sense as the function doesn't
exist anymore, so get rid of it as well.
Allow custom filters with wildcard attributes, so that clients
can support some random `filter=foo` in a .gitattributes and look
up the corresponding smudge/clean commands in the configuration file.
Function was added in commit 2c982daa2e on October 5, 2011,
and removed in commit 41fb1ca0ec on October 29, 2012.
Given the length of time it's gone unused, it's safe to remove now.
