setStereoMode

Sets what the two front speakers play (#462): each its own side, both the average of the two, both the left or both the right, or the two swapped. It acts after the downmix, so a surround film folded to two speakers obeys it too. A change crossfades, so it never clicks, and is heard once the audio already buffered has played, as a setBalance change is. Published as PlayerSnapshot.stereoMode.