Remove use of deprecated g_type_init () ...

... and bump GObject requirement accordingly.

https://bugzilla.gnome.org/show_bug.cgi?id=686318

src/main.c

@@ -361,8 +361,6 @@ main (int argc, char **argv)
   int ecode;
   TpDebugSender *sender;
 
-  g_type_init ();
-
   bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);
   bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
   textdomain (GETTEXT_PACKAGE);