display: Simplify checks to see if a window is the root window
display: Return TRUE when we've handled an X event appropriately

We need to do this to make sure events aren't improperly sent
to Clutter in the next commit.
display: Don't grab the window actor's key focus

This breaks gnome-shell's actor tracking code.
display: Always use the key focused window for key events

We no longer grab the actor's key focus, so this is necessary.
keybindings: fix per window keybindings

We must spoof events to clutter even if they are associated
with a MetaWindow, because keyboard events are always associated
with one (the focus window), and we must process keybindings
for window togheter with the global ones if they include Super,
because we're not going to see them again.