entropy: white-space nits
entropy: rename encodeBinContext to bitsCodeBin, make const

The function is not modifying the context, so there is no need to pass as a
reference, and the function can be const. Also, group the bit counting RDO
functions together
entropy: use bitsCodeBin in intra mode bit estimate functions
entropy: inline bit counting functions
entropy: inline methods which mapped to encodeBin() calls
entropy: ensure X265_CHECK() has braces
entropy: nit