Public issue https://github.com/mackron/miniaudio/issues/199

This phrase now has some negative connotations. They just had to ruin
it, didn't they?!

This bug is that the function is never returning MA_SUCCESS even when
successful.

This should fix a deadlock when uninitializing a sound after it's
reached the end.

Fix some VC6/2003 errors

This commit fixes an issue where the optimized mono expansion path is
never hit.

This is happening because the data buffer is incorrectly being reported
as busy (still loading) which is used to indicate to the engine that no
data is available and therefore nothing can be played.

This was always returning the input frame count rather than the number
of frames processed.