Update textproc/libfastjson to 0.99.4.

0.99.4 2016-08-03
- fix tautology comparison in tautology in
  `fjson_object_iter_equal`
  Thanks to Andres Stieger for the patch
- improve build system to handle slightly older autoconf versions
- fix build problems with gcc6
  Thanks to Andres Stieger for the patch

0.99.3 2016-07-11
- new dependency: autoconf-archive
- exit() is no longer called in unexpected situations
  The previous code called exit on some occasions and did not
  give the caller a chance to do any cleanup or handling on
  it's own. This has completely been removed. Note that it was
  very unlikely that this problem affected a caller, as exit()
  was only called under very rare circumstances (e.g. OOM).
- fjson_version now returns configure VERSION
  This avoid inconsistency.
- removal of Windows and Android bits
  Thanks to Michael Biebl for the patch.
- fixes of the build system
  Thanks to Michael Biebl for the patch.
- dropped support for Windows and Android as we do not target
  these platforms
- "make distcheck" now works
- fix invalid Unicode representation for some non US-ASCII
  characters when printed as string. Note that this could
  potentially also lead to a segfault

(fhajny)