* Add GET_THROTTLE_STATE environment callback
* Add RETRO_THROTTLE_UNBLOCKED
to report the case where neither vsync nor audio is limiting the call rate.
Also fix reporting of some special cases when the menu is open.
* Change throttle state mode to unsigned
Use #defines Instead of the untyped C enum to allow easier future additions.
* Spelling fixes
* Avoid any divide-by-zero