analysis: split flag cost is added only if the depth is less than max depth

removes (some) CHECKED_BUILD errors.
pixel: add signed accumulators, these were causing errors in new primitives
analysis: fix for --rd 0, always generate chroma prediction for best merge
search: nit
cu: move more statistics into FrameData
framedata: add pointer to active param structure for that picture

today, this is always the single global param. in the future it may be different
search: cleanup
analysis: only call checkDQP once per CU, use a consistent reconPic write policy
analysis: nits
search: --pme needs master instance to be passed to slave function

The slave was read its own m_listSelBits instead of those pre-computed by the
master, and then even worse it was updating its own m_bestME (holding its own
output lock) instead of the master's.
analysis: try lossless encode of only the best mode for each CU

This involved some subtle changes in behavior. TComDataCU::initCTU and initSubCU
now initialize m_cuTransquantBypass to the global --lossless flag, so in the
first pass of analysis it will always be all non-lossless (typical) or all
lossless (when --lossless is enabled).

Before this change, when "--cu-lossless and !--lossless" the encoder would try
both lossless and non-losseless coding of every option evaluated for RDO.
This roughly doubled the work performed by the encoder, and because the same
TComDataCU instance was being used for both, it was fragile

After this change, the encoder will only try lossless once per CU using the
best mode found during non-lossless RDO, using a seperate TComDataCU instance.
cu: re-order part data defines to match allocation order (nit)
cu: clear transform skip flags in lossless CU copy
analysis: share the depth, best modes and partitions based on cuAddr - bug fix
weighted prediction pixel, interface simplification
rc: fix error in vbv due to access of unreferenced refFrame data
analysis: copy inter prediction when evaluating lossless
analysis: do not try lossless if best mode had no distortion
doc: update description of --cu-lossless