This patch implements the Xv extension for VMware's X video driver.
The Xv specification can be found here
http://www.xfree86.org/current/DESIGN16.html
I've written a trivial offscreen memory manager that allocates memory from the
bottom part of the Video RAM and it can handle only 1 video-stream. Eventually
we intend to support upto 32 video-streams (there is already support for
multiple video streams in respective backends).