Document code_800F9280.c -> audio_seqcmd.c i.e. (Audio_QueueSeqCmd)

[engineer124]

This documents code_800F9280.c which primarily deals with high-level audio sequence commands that allow sequences to be modified in real-time, via the function Audio_QueueSeqCmd(). Wrappers for this command are provided in a new header called seqcmd.h, there are 33 separate commands available to use!

The casting is quite picky for matching so I avoided the _SHIFTL macro's, so I'm not too sure what's preferred. I just avoided it all together for now.