GTK2 fixes:
- Fix toolbar styling in Eclipse/SWT
- Fix completion tooltips styling in Eclipse/SWT
- Fix a bug rendering menus in Opera
- Fix missing shadow for frames with embedded labels
- Fix missing SELECTED states for check/radio assets
- Make it possible to override GtkEntry's background color
- Fix stray shadow for frames with GTK_SHADOW_NONE
- Workaround an OpenOffice.org scrollbar rendering bug
- Require GTK+ 2.24.15 and 3.6.2
