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/core.c

@@ -348,7 +348,7 @@ meta_core_lower_beneath_focus_window (Display *xdisplay,
                     xwindow,
                     CWSibling | CWStackMode,
                     &changes);
-  meta_error_trap_pop (display, FALSE);
+  meta_error_trap_pop (display);
 }
 
 void