Do not use deprecated AM_PROG_CC_STDC

https://bugzilla.gnome.org/show_bug.cgi?id=736180
Remove setting pty to blocking

https://bugzilla.gnome.org/show_bug.cgi?id=736181
Added m4/vapigen.m4

https://bugzilla.gnome.org/show_bug.cgi?id=736179