Adding option to use variable timestep by defining FLX_NO_FIXED_TIMESTEP
Renaming FLX_NO_FIXED_TIMESTEP to FLX_VARIABLE_TIMESTEP.
Replace FLX_VARIABLE_TIMESTEP by static var FlxGame.fixedTimestep, don't disable the vcr when using variable timestep
Merge pull request #5 from Gama11/dev_timestep

Replace FLX_VARIABLE_TIMESTEP by static var FlxGame.fixedTimestep, don't...
Merge pull request #526 from crazysam/dev

Adding option to use variable timestep