Converting to SDL2

This initial release is ready. cata_tiles will need to be tweaked later to conform to SDL2 better. Uses a simple patch on that part of the code for the moment. Shouldn't have any issues.

Tested build and run on Windows for SDL Tiles and SDL Curses.
Tested build and run on Linux for SDL Tiles by cib0.

This may require tweaking Jenkins to be able to build it (I know nothing about that).