lua_playerlib.c

* Store gravflip (resolves #206) and destscale in starposts. (Using the same field, taking advantage of the fact that object scale will always be positive!)
* Update the function signature of P_MixUp to accomodate both it and drawangle instead of doing it outside of the function.
* If the player is spawning from the start of the stage and it's from the ceiling, be in fall frames as requested (resolves #191).