Updated SConscript to SDL2
Started porting to SDL2, non working code is marked with '#ifdef OLD_SDL1'
Implemented basic drawing operations for SDL2
Added cleanup to SDLFramebuffer and fixed clipping
Fixed crashing due to scancode/keycode mixup
Enable BLEND render mode, fixed incorrect color on rect and line drawing
Fixed another scancode/keycode issue
Fixed window title and icon
Copy all surface flags in Blitter::create_surface_from_format()
Fixed up some colorkey handling
Some fixes to fullscreen mode, somewhat incomplete
Added missing <sstream>
Removed some unused code
Fixed screenshoting for SDLFramebuffer, removed HAVE_OPENGL define
Use SDL_GetRendererOutputSize() instead of window size for screenshots
Swapped Screenshot subpixels around
Implemented mouse grab stuff for SDLFramebuffer
Implemented SDL2 text/unicode handling
Fixed another scancode/keycode mixup
Fixed keyboard->button mapping