Also support dynamic/static opengl switching

It is really messy at the moment. There is no support for copying the
necessary frameworks and dylibs out to the bundle for distribution, and
it is a frankenstein of manual find_library and find_package which can
sometimes pick up Homebrew dylibs.

Compiles the SDL2 target on Windows successfully

Alam Ed Arias authored 10 years ago and Alam Ed Arias committed 10 years ago

Make sure clear_conditionsets feeds in 1 to MAXCONDITIONSETS instead of 0 to MAXCONDITIONSETS-1, so that M_ClearConditionSet can use them all properly AND clear all condition sets properly.

Apparently the mistake also caused myargc to be cleared in Linux64 SDL2 (as pointed out by that ilag11111 guy on GitHub), so that should be fixed now too.

Also made fades use core functions if they are available.

MOUSE6-8 will not be supported on SDL2 as there is no interface for them.

ONLY US KEYBOARDS SUPPORTED! THAT'S HOW WE DO IT IN AMURRICA

In some cases, the warp back to center was being detected as a mouse motion, causing all sorts of silliness with the mouse. The workaround is by only using the first motion event and ignoring every event after that, until the next call to I_GetEvent.