Improved mb_lpf_horizontal_edge_w_sse2_8

This patch is a reformatted version of optimizations done by
engineers at Intel (Erik/Tamar) who have been providing
performance feedback for VP9.  For the test clips used (720p, 1080p),
up to 1.2% performance improvement was seen.

Change-Id: Ic1a7149098740079d5453b564da6fbfdd0b2f3d2
Added per pixel inter rd hit count stats

Added some code to output normalized rd hit count stats.
In effect this approximates to the average number of rd
operations/tests per pixel for the sequence.

The results are not quite accurate and I have not bothered
to account for partial SB64s at frame edges and for key frames
However they do give some idea of the number of modes /
prediction methods being tested for each pixel across the
different partition sizes. This indicates how much scope their
is for further gains either by reducing the number of partitions
examined or the modes per partition through heuristics.

Patch 3 moved place where count incremented so partial rd
tests that are aborted with INT_MAX return are also counted.

Example numbers for first 50 frames of Akiyo.
Speed 0 ~84.4 rd operations / pixel
Speed 1 ~28.8
Speed 2 ~11.9

Change-Id: Ib956e787e12f7fa8b12d3a1a2f6cda19a65a6cb8
Refactor 16x16 unit tests

Make the new test module comply to the unit test rules.

Change-Id: Id79ff7f03f870973ffbc74f26d64edb418b75299
Fix intermediate height in convolve_c

- Intermediate height was not correct i.e. when block size is 4 and
  y_step_q4 is 6. In this case intermediate height was
  (4*6) >> 4 = 1 and vertical interpolation needs two source pixels
  plus 7 extra pixels for taps.
- Also if the current output block is 16x16 and we are using 4x upscaling
  we need only 12 rows after horizontal filtering instead of 16.

  Patch Set 2: Intermediate_height updated after CL 66723
               "Fix bug in convolution functions (filter selection)"

Change-Id: I5a1a1bc2ac9d5edb3a6e0818de618bf318fdd589
Merge "Refactor 16x16 unit tests"
Merge "Added per pixel inter rd hit count stats"
Fix 32x32 forward transform SSE2 version

This commit fixed the potential overflow issue in the SSE2
implementation of 32x32 forward DCT. It resolved the corrupted
coded frames in the border of scenes.

Change-Id: If87eef2d46209269f74ef27e7295b6707fbf56f9
Merge "Improved mb_lpf_horizontal_edge_w_sse2_8"
Merge "Fix 32x32 forward transform SSE2 version"
Merge "Fix intermediate height in convolve_c"