Add TR_MAX_WIDTH.

- Max transform size is constrained by but independent of LCU size.

- Luma and chroma now have the same stride for transform arrays.
Expand chroma functions to parent function.

- This was done so that making the function work with luma would be easier.
Move luma quantization to it's own function.
Remove abs_sum from coeff quantization.

- It's meant for checking if there are any coefficients, but we don't use it
  and it's annoying to remember to initialize it and pass it around. The
  benefit should be quite small anyway.
Clean up coeff reconstruction code.
Make luma and chroma use the same quantization function.

- Only thing not working was transform skip.
Add new implementation for trskip decision.
Move new trskip decision to a function.
Clean up trskip decision code and remove old code.

- You can define structs inside functions! This changes everything!!

- Bitstream changes a little bit compared to old trskip decision. Bdrate
  change is insignificant though.
Merge branch 'coeff_cleanup'