gstring: Mark g_string_free() as taking (transfer full) input
gstring: Mark g_string_free() as taking (transfer full) input

This is unusual, but the correct annotation for a free() function.

https://bugzilla.gnome.org/show_bug.cgi?id=742903

tchakabam/glib,mzabaluev/glib,ieei/glib,ieei/glib,tchakabam/glib,tchakabam/glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,cention-sany/glib,cention-sany/glib,tchakabam/glib,endlessm/glib,cention-sany/glib,mzabaluev/glib,mzabaluev/glib,Distrotech/glib,cention-sany/glib,Distrotech/glib,mzabaluev/glib,MathieuDuponchelle/glib,tchakabam/glib,MathieuDuponchelle/glib,ieei/glib,endlessm/glib,cention-sany/glib,Distrotech/glib,ieei/glib,johne53/MB3Glib,johne53/MB3Glib,MathieuDuponchelle/glib,Distrotech/glib,endlessm/glib,johne53/MB3Glib,ieei/glib,MathieuDuponchelle/glib,Distrotech/glib,mzabaluev/glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib