Add xinerama support to the vmware video driver. (Better late than never).

Add xinerama support to the vmware video driver. (Better late than never).

With this change, the VMWARE_CTRL extension is updated so that it can
receive topology updates at runtime. I will add some sample client code
separately.

I also intend to add support for a static initial topology defined in
xorg.conf but I haven't got around to it yet due to hating to write
string parsing code.