Use a helper function to check valid MIDI controller inputs
Make some more functions static
Fix a couple checks
Avoid aliasing an int array
Don't set modulators that have no destination
AL_SOFT_source_length is complete
Don't require pre-declaring vector types
Allow ALsoundfont_deleteSoundfont to handle multiple buffers
Use VECTOR_FIND_IF instead of a manual loop
Regroup and reorganize some macros
Store 4 modulators per map entry
Rename some functions
Access the result macro parameter only once
Add a source radius property that determines the directionality of a sound

At 0 distance from the listener, the sound is omni-directional. As the source
and listener become 'radius' units apart, the sound becomes more directional.

With HRTF, an omni-directional sound is handled using 0-delay, pass-through
filter coefficients, which is blended with the real delay and coefficients as
needed to become more directional.
Fix omni-directional moving HRTF coeffs