Port reading Motif hints to XCB
Review Request #122378 - Created Feb. 2, 2015 and submitted
A wrapper class for MotifHints is added to xcbutils. This class manages
the information about the read Motif hints, so that Client doesn't need
to have a copy of the read states.
The class is designed in a way that during Client::manage we get rid of
See added unit test.