Remove compatibility for GTK+-2.0

While the Meego developers agreed to switching mutter to GTK+-3.0
unconditionally a while ago, Canonical used a GTK+-2.0 build for their
Unity project. As Canonical now announced a switch to compiz as their
window manager, there is no longer a reason to maintain GTK+-2.0
compatibility.

https://bugzilla.gnome.org/show_bug.cgi?id=633133

src/core/main.c

@@ -623,9 +623,6 @@ main (int argc, char **argv)
 
   g_option_context_free (ctx);
 
-  /* must be after UI init so we can override GDK handlers */
-  meta_errors_init ();
-
   /* Load prefs */
   meta_prefs_init ();
   meta_prefs_add_listener (prefs_changed_callback, NULL);