Add missing checks for gnulib vasnprintf()
Add missing checks for gnulib vasnprintf()

Commit 212e4232e7520b2e328e3e965ed792e17b12e144 introduced a big update
of gnulib. Necessary changes to configure.ac from old gnulib commit
e8e63d1b31bca6c82713cba490b21a861abb24b5 have been forgotten. Actually
available functions are not discovered by autotools.

https://bugzilla.gnome.org/show_bug.cgi?id=759134

Distrotech/glib,endlessm/glib,MathieuDuponchelle/glib,mzabaluev/glib,johne53/MB3Glib,mzabaluev/glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,mzabaluev/glib,johne53/MB3Glib,mzabaluev/glib,Distrotech/glib,mzabaluev/glib,endlessm/glib,MathieuDuponchelle/glib,endlessm/glib,Distrotech/glib,johne53/MB3Glib,Distrotech/glib,endlessm/glib,MathieuDuponchelle/glib,MathieuDuponchelle/glib,johne53/MB3Glib,Distrotech/glib,MathieuDuponchelle/glib