- 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.
Also simplified the sound init decision making. With FMod gone there is no reason to be pedantic here. Even the check of snd_backend for the Null device could be omitted here, its only realistic use is '-nosound'.
Many of the simple wrappers have been moved to a separate file and the sound source handling has been abstracted.
This is only the first phase, the work is not complete yet.
Also changed the license of the sound code to BSD after verifying that this code bears no similarity to id's original sound code anymore, save for a few function names (which are due to be refactored out anyway.)
Now there is only one single entry point for both, instead of previously 2 entry and 4 exit points.
This also eliminates the explicit shutdown of ZMusic. Timidity++'s two buffers have been put in containers that self-destruct on shutdown and calling dumb_exit is not necessary because the only feature requiring it is not used by any code in the music library.
This was the last player class.
This code was also cleaned up for non-Windows systems where CD Audio is not implemented.
Instead of providing an empty implementation, all related code is now explicitly deactivated.
