Switched to Clutter 1.2

[Owen Taylor <otaylor redhat com>]

I've now landed patches in gnome-shell and Mutter to support and require
the recently released Clutter 1.2 version. Some notes:

 * If you are using the build instructions from 
   live.gnome.org/GnomeShell, then there are some issues in switching
   to the correct branch of Clutter. (*) The recommended procedure 
   for updating:
 
    # Remove the old Clutter checkout
    rm -rf ~/gnome-shell/source/clutter
    # Build all modules from scratch
    jhbuild build -afc

 * Clutter-1.2.0 doesn't properly handle the GL_TEXTURE_RECTANGLE_ARB
   extension that is required to get gnome-shell working on some
   hardware (in particular on Radeon 3xx and Radeon 5xx chips)
 
   Some fixes for this have been landed in Clutter Git, but there is
   still one outstanding.

   (http://bugzilla.openedhand.com/show_bug.cgi?id=2016)

 * With the Radeon driver I'm also seeing a problem where when a 
   window is resized it draws at the new size as black, then draws
   correctly. I haven't tracked this down yet, so I'm not sure if
   it's a driver bug or a Clutter/Mutter bug.

Try it out, report new problems you find. There are likely some rough
edges that will take a few days to sort out.

- Owen

(*) jhbuild doesn't handle the branch switch perfectly, and there are
some leftover stale files in the build tree that can cause problems.