* gave reverb functions the proper 'S_' prefix for consistency.
* Blood: fixed license of 4 files which do not contain any NBlood code anymore (sound code was completely rewritten, and all such code has long been moved out of d_menu.cpp)
* Blood: renamed VIEWPOS_* constants
This still passed the sprites instead of the actors. Moved the relinking code to DCoreActor::Destroy because it is the same for all games.
Also did a little bit of sound cleanup to ensure the sound backend does not hold stale actor pointers.
Parts of the sound system treat entry 0 as "no sound" so nothing placed there would play.
This made the one custom sound in "The Way of Ira" not play because as the last sound being defined it ended up in the first, invalid slot.