Composite uses an unmap/map cycle to trigger backing pixmap allocation
and cliprect recomputation when a window is redirected or unredirected.
To avoid protocol visible side effects, map and unmap events are
disabled temporarily. However, when a window is unmapped it is also
removed from grabs and loses focus, but these state changes are not
disabled.
This change supresses the unmap side effects during the composite
unmap/map cycle and fixes this bug:
http://bugzilla.gnome.org/show_bug.cgi?id=488264
where compiz would cause gnome-screensaver to lose its grab when
compiz unredirects the fullscreen lock window.
a6a7fadbb0