It's not available as an AL buffer format (yet) since I'm not sure how to
expose it. Internally it seems fine as a separate channel configuration, but
because OpenAL combines the channel configuration and sample type, a flag may
work better there.
This attempts to correct for the differences needed for 2-channel UHJ's shelf
filters given the output shelf filters. It's far from ideal, but better than
nothing.
There's now effectively a 16-channel limit for buffers (as determined by the
number of elements in DeviceBase::mSampleData). Any more than that are
ignored when mixing.
