[mythtv] Video Output patch (incl. Windows & OSX) v10

[Daniel Kristjansson]

This is an update on the Xv/XvMC patch.
The patch is here:
   http://www.mrl.nyu.edu/~danielk/mythtv/xv-xvmc-merge-v10.patch.bz2

It adds fixes for OS X compilation, and fixes a segfault detected by
Robert Johnston. It has some known problems:

 1/ It does not work for MPEG-TS recordings.
 2/ It does not work for non-MPEG recordings when XvMC is available.
 3/ There is an OSD or pause issue which can cause hard lockups on
    some systems with a GeForce4 MX GPU.

This patch also ads more doxygen documentation for the VideoBuffers
and VideoOutput classes.

-- Daniel