These signals were in the uncompressed frame header (as a temporary
hack), which caused two problems:

* We don't want that header to be duplicated in the slice header
* It was necessary to signal the number of bits to transmit up front

However, the filter size can be 128x128 which is greater than the SB
size, and a decoder wouldn't be able to know whether to read a bit or
not until the final SB of that 128x128 block has been decoded
(depending on whether the 128x128 is all skip or not).  Therefore the
signalling was changed for 128x128 blocks so that every top left SB of
a 128x128 filter block contains a signal regardless of whether the
block is all skip or not.  Also, all the MB's of 128x128 block are
filtered even if they are skip MB's.  This gives the signal a purpose
even when the 128x128 block is all skip, and it also gives a slight
coding gain as it leaves a way to filter skip blocks, which was
previously forbidden.

Low latency:
PSNR YCbCr:     -0.19%     -0.14%     -0.06%
   PSNRHVS:     -0.15%
      SSIM:     -0.13%
    MSSSIM:     -0.15%
 CIEDE2000:     -0.19%

High latency:
PSNR YCbCr:     -0.03%     -0.01%     -0.09%
   PSNRHVS:      0.04%
      SSIM:      0.00%
    MSSSIM:      0.02%
 CIEDE2000:     -0.02%

Change-Id: I69ba7144d07d388b4f0968f6a53558f480979171