Revert "Remove SDL build dependency."

[Narann]

Reverts #14

SDL1.2 internal state is not initialized before calling SDL_ functions #15

It seems 87ef789 from pull request #14 broke the SDL1.2 initialization. On parts of the platforms the main function must be replaced and instead the private SDL-main (parachute) function has to be called first. This is the only use of this SDL_main.h include. The programs main function is redefined as SDL_main and the main function is included using a special static library. The normal startup will therefore be main(SDLmain.a) -> SDL_main(previously known called main in the actual program source code). Of course, main() is not always called main() but I just use it here as placeholder for the real name.

This special indirection is required to initialize the internal state of SDL before the actual program calls any SDL function.

A similar problem already caused the windows builds to break (in a very hard to debug way) in the past.

[littleguy77]

@Narann I don't think the formality of a PR is needed here. I meant to suggest that you revert the master branch directly since you have write privileges.

[Narann]

The github "Revert this PR" feature imply a PR actually. :)