There were two booleans that could be merged into the flag word.
This also fixes a bug with CHAN_NOSTOP not working for local sounds because it checked the wrong sound source for the playing sound.
- 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.