Jan Alexander Steffens authored Dec 05, 2018 and Sebastian Dröge committed Dec 05, 2018

The latter is going away in libfdk-aac 2.0.0. Instead, MPEG-style output
is always non-interleaved and WAV-style output is always interleaved.
Earlier libfdk-aac also defaults interleaving accordingly.

Since our reordering looks at the associated PCE indices instead of the
actual channel order, we're agnostic to the mapping.

For #825