replaced play_sound_cooldown with play_sound_ex. it now has a new
parameter: bool replace. if true, the sound will interrupt the previous
instance of itself being played, if any. if used many times in
succession, this effectively allows one to "restart" a sound instead of
letting many instances overlap. this sounds better in some instances,
and avoids flooding the channels.
this is also implicitly true for play_ui_sound now.
normalized sound effects, converted them to ogg vorbis. there's now a
global config file sfx/volumes.conf, where the volumes of sound effects
can be adjusted. the default volume is 100, the max is 128.
load_textures() was changed to load_resources() and will now load all sounds in sfx/. playing via play_sound(char *name) (or the pointer variant). positional audio is not implemented yet.
and some other changes.
