KbWait: Add workaround for MS-Windows "app not responding" timeout trigger.

Add a useless call to GetMouse() in the wait loop, which will in turn
trigger event processing of the applications event queue to avoid
white-out problems due to hitting the 10 seconds "Application not
responding" timeout if we don't poll the event queue often enough. It's
a sad world Windows users have to live in...
Screen for 32-Bit Matlab on Windows rebuilt for testing.

So Matthew can test the GStreamer DV-Camera hacks.