* code the palette color index using 45 wavefront
* interleave the coeff and palette color index in
  transform block level
* the above change does not change code efficiency

Details: 
The 45 wavefront scan allows to compute the ctx of
the diagonal samples' indices  at the same time. 
Interleaving palette indices and palette residual
on a transform block basis means that the entropy
 decoding and further processing of the palette 
residual is not delayed by the entropy decoding 
of all the color indices of the palette encoded 
block.
Change-Id: Ie9f576002a9a68394b99c23b01e9730df06df070