Removed fork of ext/zlib/tests/bug_52944.phpt

The real issue is a bug in asm zlib build, reported here
https://github.com/madler/zlib/issues/41 . Non ASM builds
behave more predictable.
gd: provide imageflip with system libgd when available
Merge branch 'PHP-5.5'

* PHP-5.5:
  gd: provide imageflip with system libgd when available
Merge branch 'PHP-5.5'

* PHP-5.5:
  Removed fork of ext/zlib/tests/bug_52944.phpt
Merge branch 'master' of git.php.net:php-src
gd: fix proto comment