Right now we handle buffer releases coming from the
compositor in a central place. We add a listener when
first creating the shared buffers.

This is problematic because a buffer can only have
one listener on it at once so users of the buffer
can't get notified when it's released.

This commit moves the buffer listener code from the
centrally managed display code to the cursor and window
code.

https://bugzilla.gnome.org/show_bug.cgi?id=761312