Added sdl2 m4 macros.
Added sdl2 m4 macros.

libavg/libavg,libavg/libavg,hoodie/libavg,th3infinity/libavg,hoodie/libavg,libavg/libavg,hoodie/libavg,libavg/libavg,th3infinity/libavg,th3infinity/libavg,th3infinity/libavg,hoodie/libavg