lossy encoding: ~3% speed-up

incorporate non-last cost in per-level cost table

also: correct trellis-quant cost evaluation at nodes
(output a little bit different now). Method 6 is ~4% faster.

Change-Id: Ic48bd6d33f9193838216e7dc3a9f9c5508a1fbe8
speed-up trellis quant (~5-10% overall speed-up)

store costs[] in node instead of context

Change-Id: I6aeb0fd94af9e48580106c41408900fe3467cc54
also: various cosmetics
Merge "lossy encoding: ~3% speed-up"
Merge "speed-up trellis quant (~5-10% overall speed-up)"
Refactor GetBestPredictorForTile for future tuning.

This change doesn't impact compression gain or compression speed.

Change-Id: Ia87d8a46c6f1ce0f8974178d75a6b0ba0a6e3696
Merge "Refactor GetBestPredictorForTile for future tuning."
cosmetics: normalize VP8GetCPUInfo checks

- use '!= NULL'
+ dec_neon/STORE_WHT: align '\'s

Change-Id: I0f0ce49bd9c58e771bafb24c51c070d5ebd77e53
5-10% encoding speedup with faster trellis (-m 6)

mostly by:
- storing a single rd-score instead of cost / distortion separately
- evaluating terminal cost only once
- getting some invariants out of the loops
- more consts behind fewer variables

Change-Id: I79451f3fd1143d6537200fb8b90d0ba252809f8c
Merge "5-10% encoding speedup with faster trellis (-m 6)"
Refactor code for HistogramCombine.

Refactor code for HistogramCombine and optimize the code by calculating
the combined entropy and avoid un-necessary Histogram merges.

This speeds up lossless encoding by 1-2% and almost no impact on compression
density.

Change-Id: Iedfcf4c1f3e88077bc77fc7b8c780c4cd5d6362b
few cosmetics after patch #69079

Change-Id: Ifa758420421b5a05825a593f6b43504887603ee7
Merge "few cosmetics after patch #69079"