Log Message:
Update liblangtag to 0.5.8:

0.5.7 -> 0.5.8
=================
Akira TAGOH (6):
      Fix the build fail on MSVC 14 (fixes issue#13)
      Drop the word of GNOME from the ifdef'd variable for debugging
      Fix the build requirement in pkgconfig file
      Make some header files public (fixes: issue#14)
      Fix test fail on SunOS
      Fix unknown node issue