Pulling x264 weight decision into x265 lookahead
Using weighted lowres ref frames in cost estimation in lookahead
slicetype: optimize away mcWeight helper function
slicetype: since w is an auto-var there is no need to zero at early-outs
slicetype: use x265 style camelCase auto vars
slicetype: remove unnecessary lines, simplify a few things
slicetype: correct non-denom round, improve some comments