Do not leak a cairo region

This memory leak fix was present in GTK+ 3 since 3.10. We forgot
to backport it to GTK+ 2.

https://bugzilla.gnome.org/show_bug.cgi?id=738837
Ignore gdk-pixbuf deprecations

We're not going to start updating the 2.24 branch to newer
gdk-pixbuf APIs, so ignore deprecations.
Merge branch 'gtk-2-24' of git://git.gnome.org/gtk+ into gtk-2-24