Update all the screen related stuff.

I tried to substitute all the 'screen' related code with the new SDL2 renderer
stuff. I keep having a 320x200 surface which is blitted into, and this ends up
in a streaming texture which is then rendered. I try to make use of the render
logic size, but of course I could not test anything of this.
Fix definition collision and more sdl_setcolors.
Comment out some zoom stuff that I don't think I need.
Comment out some non-compiling input code.

I'll have to come back and review it, I just consider non essential for now.
Update code to get available vide modes.