Add --tr-depth-intra command line option.

Conflicts:
	src/encoder.c
Rebase transform split search.
Add --rd=3 mode and enable searching of intra depth 0.

- intra_build_reference_border was overflowing at depth 0 because it uses
  arrays just large enough to accommodate 32x32 transforms, which is the
  biggest transform.
- For similar reasons search_intra_rough doesn't work at depth 0.
- The --rd=3 mode tries all modes with transform search. It also works without
  rough search so it was used to test depth 0 search. If --rd=3 is not on intra
  split at depth 0 is not searched for.

Conflicts:
	src/search.c
Fix transform split search.

- Redo the search with the best mode to make sure the tr_depth parameters are
  correct.
Simplify cabac context copying.

Conflicts:
	src/context.c
Add missing cabac context for chroma cbf.

- The context was also missing from HM, but has been fixed in HM13.
test cu split cost
Add cabac bit costs float table.
Added cabac bit cost calculations to SAO search
SAO merge checking cleanup
Check SAO band offset for both chroma components and better SAO chroma cabac costs
Implemented SAO search for both chroma components
Improved SAO merge decisions
Fix compiler warnings.

- Non-parenthesized parameter in a macro.
- Unused variables.
- Wrong const qualifiers.
- Signed/unsigned comparison.
Merge branch 'sao_cabac'