Add libxcb-util-wm
Summary
Add libxcb-util-wm as X11 Qt apps need it.
Reasoning
For successful backwards-compatibility, we will need to add this library. QT_DEBUG_PLUGINS=1
on a Qt app eg. Gaffer fails to launch, as the xcb
plugin fails to load as it is after libxcb-icccm
which is a part of libxcb-util-wm
.