Have CABAC_BIN accept any >0 as binary 1.

It used to treat odd numbers as false.
Remove unnecessary tertiary expressions from usages of CABAC_BIN.
Improve cu_info coded block flag data structure a bit.

- It works just like the old structure except that the flags are checked with
  bitmasks instead of having the flag value be propagated upwards. There isn't
  really any benefit to this because the flags still have to be propagated to
  parent CUs.

- Wrapped them inside a struct to make copying them easier. (Just need to copy
  the struct instead of making individual copies)
Clear old cbf data before recursion in encode_transform_tree.

- Because encode_transform_tree also maintains the CBF data and assumes that
  the CBFs are initially zeroed, calling the function more than once would
  result in incorrect CBF data.