SAGE vo driver file and configuration

SAGE is an opensource project, licensed with New BSD License. It provides an API and software to set up a tiled multidisplay with extremely high resolutions. More information you can find at http://www.sagecommons.org/
There was driver for mplayer in their repository, made only for one fork. I think it is better to pull this driver into main tree. In fact I've already done ports to mplayer2, and tested this on OpenSuSE 12.1.
As you can see, all structure has left stable and untouched except additions for driver, wrapped into defines, calculated from ./configure.

Additional change was in libvo/video_out_internal.h. See inline commit comments for more information.