weight: match x264 weight analysis and logging [OUTPUT CHANGE]

This only weights the first reference, and will only weight chroma if luma
was weighted. Further work remains, we must add an unweighted dup of the
weighted reference into the P slice's L0 reference list.
TEncSearch: cleanups in predInterSearch(), no logic change
TEncSearch: remove useless distBiP argument from xEstimateMvPredAMVP
TEncSearch: replace costbi with listCost[2]
TEncSearch: rename bits to listbits[] for clarity
TEncSearch: simplify and localize scope of bitstemp
TEncSearch: localize scope of costTemp
TEncSearch: localize scope and rename listRefIdx
TEncSearch: localize scope of mvzero
TEncSearch: localize scope and rename listMv
TEncSearch: remove mvTemp[][] array, just use outmv stack var
TEncSearch: localize scope, rename, and remove defaults for listSelBits array
TEncSearch: remove list1 hacks
TEncSearch: hoist bMergeOnly check to only be performed once

--HG--
extra : amend_source : 7ff15f0f5eca9ac34a07f03edf7291558ca31f36
TEncSearch: localize scope of bidir MV and ref idx arrays
TEncSearch: host bMergeOnly logic to the top of predInterSearch

This makes merge-only easier to follow and more efficient, and makes the full
search code easier to read and easier to maintain.  This should have no change
in outputs

--HG--
extra : amend_source : 618ca45b506e775af2677053045a70dd3ba0c006
TEncSearch: reorder code for more clarity
TEncSearch: fix some comments