Blender Git Loki

Remove SDL_VIDEODRIVER=dummy environment variable setting, this may interfere
with other applications launching SDL applications from Blender.

At the time this was added the game engine joystick code was unnecessarily
initializing the SDL video subsystem, and looking at the SDL source code that's
the only place this environment variable is read. That doesn't happen anymore,
though we do have WITH_GHOST_SDL now. But the environment variable is set after
GHOST has been initialized, otherwise this code would have actually broken that.