Port to SDL 2.

Can someone please test this on windows? I could not get the included SDL nor the included Boost (does not correctly detect gcc's threading support) to work. It works like a charm with the current libsdl2-dev 2.0.0+dfsg1-3 in debian testing though.

This also fixes a bug when requesting multisampling when its not available and adds a few missing source files to the project file.