Updating the video converter

After thorough deliberation, we're announcing that we're about to drop the ffserver program from the project starting with the next release.

ffserver has been a problematic program to maintain due to its use of internal APIs, which complicated the recent cleanups to the libavformat library, and block further cleanups and improvements which are desired by API users and will be easier to maintain.

Thanks also to Google for this wonderful program and to everyone that made room in their busy lives to help making GSo C2016 a success. Support for the SDL1 library has been dropped, due to it no longer being maintained (as of January, 2012) and it being superseded by the SDL2 library.

As a result, the SDL1 output device has also been removed and replaced by an SDL2 implementation.

The design and implementation is based on the snow video codec, which uses OBMC.