Add a new win32 videosink. Uses the DirectShow renderers for high-performance video rendering on win32.

Original commit message from CVS:
* configure.ac:
* sys/Makefile.am:
* sys/dshowvideosink/Makefile.am:
* sys/dshowvideosink/README:
* sys/dshowvideosink/dshowvideofakesrc.cpp:
* sys/dshowvideosink/dshowvideofakesrc.h:
* sys/dshowvideosink/dshowvideosink.cpp:
* sys/dshowvideosink/dshowvideosink.h:
Add a new win32 videosink. Uses the DirectShow renderers for
high-performance video rendering on win32.
Currently only supports some YUV formats.
Rank PRIMARY, since it's much more useful for the common cases that the
directdraw sink (which only does RGB).