Bug 651224 - Potential NULL display ptr from quartz gtk_clipboard_wait_for_contents
gdkwindow: Handle references in "update_windows" list correctly

Since update_windows list is a static variable in GdkWindow.c which
contains pointers to windows which needs to be updated, it can happen
that it contains a pointer to a window even after quit from a gtk_main().
If another gtk_main() is called in the same process it tries to process
windows in the list which leads to a crash.
Correct reference count handling of added windows prevents such applications
from crash.

https://bugzilla.gnome.org/show_bug.cgi?id=711552
gdkwindow: Don't add the same window to "update_windows" twice

This prevents passing of such window to another GMainLoop.

https://bugzilla.gnome.org/show_bug.cgi?id=711552
Merge branch 'gtk-2-24' of git://git.gnome.org/gtk+ into gtk-2-24
Merge branch 'gtk-2-24' of https://github.com/johne53/MB3Gtk-2 into gtk-2-24