Native GTK apps in Mir

[Daniel van Vugt]

Following on from the proof of concept in May, native Mir support for 
GTK apps has landed in utopic-proposed (3.12.2-0ubuntu6):

   https://launchpad.net/ubuntu/+source/gtk+3.0

Basic stuff works but more work is required, if anyone wants to help out 
with the immediate major stuff:

1. Cursor API not implemented (several GTK apps think this as a reason 
to crash).

2. Menus and dialogs not displayed correctly.

- Daniel