Changed how UV r/d estimates are done for Intra Modes

The commit changed to compute UV intra RD estimates for 4x4 and 8x8
separately to be used in mode decision for MB modes associated with
the appropriate transform size respectively. Now finally after many
other changes related 8x8 quantizer zbin boost and zbin_mode_boost,
this change overall helps the HD(with 8x8) by around ~.13%.
(avg .13%  glb .13% ssim .17%)

The commit also has a few changes for eliminating compiler warnings.

Change-Id: Ibab35dad44820c87e6b44799c66f8d519cc37344