- added Marisa Kirisame's CHAN_OVERLAP flag.
- exported S_IsActorPlayingSomething to ZScript.
The sound API change required deprecating A_PlaySound and S_Sound. There are now new variants S_StartSound and A_StartSound which have two distinct parameters for channel and flags.
This was only run on a state change and missed every external light change.
Any place which wants to flag a light change now only will set a flag and at the end of the thinker loop all flagged actors will be processed.
For performance reasons this was merged with the P_RunEffects iterator loop.