modules/mixer: implement style=sine

This adds a common retro demo transition using
converging/diverging horizontally interlaced sine offsets to
transition to/from a_module->b_module

Some stubs have been left in place for a vertical variant, and
some TODOs for future settings/taps.  As-is it's a largely fixed
horizontal thing, introducing just the new style=sine variant
with no additionl settings or taps for now.

I particularly enjoy:

--module=mixer,style=sine,a_module=roto,b_module=roto

0 files changed, 0 insertions, 0 deletions