entropy: rename combined CABAC/SBac class to Entropy
frameencoder: explicit size conversion to avoid MSVC warning
Backed out changeset: cff4f6482385

This head was accidentally created.
Merge, discard accidental push
compress: Fixes fudging in merge costs, stores sa8d costs for bestMergeCU in m_sa8dCost
compress: save inter sa8d costs also in m_sa8dCost
compress: save intra costs in rd <= 2 also in m_sa8dCost.

Basically, all sa8d costs are always saved in m_sa8dCost.
rest: document lossless coding theory and behavior
encoder: insert missing comma
compress: fix sa8dCost comparisons.

After this patch, all sa8d costs are stored in m_sa8dCost, and RD costs in m_totalRDCost