- Slightly under-estimate cost of decoder muxes
- Prefer larger muxes at tree root at same cost
- Don't double-count input cost for partial muxes
- Add debug log output
o Not all derived methods were marked 'override', but it is a great
feature of C++11 that we should make use of.
o While at it: touched header files got a -*- c++ -*- for emacs to
provide support for that language.
o use YS_OVERRIDE for all override keywords (though we should probably
use the plain keyword going forward now that C++11 is established)