SSE2 implementation of S32_D565_Opaque_Dither

SSE2 implementation of S32_D565_Opaque_Dither

Run benchmarks with command line option "--forceDither true". The result
shows that all benchmarks exercised S32_D565_Opaque_Dither benefit from
this SSE2 optimization. Here are the data on i7-3770:
                                                  before    after
constXTile_MM_filter                              900.93   217.75  75.83%
constXTile_CC_filter_scale                        907.59   225.65  75.14%
constXTile_RR_filter                              903.33   219.41  75.71%
constXTile_MM_scale                               902.45   221.46  75.46%
constXTile_CC                                     898.55   218.37  75.70%
constXTile_RR_scale                               902.69   222.35  75.37%
repeatTile_4444_X                                 938.53   240.49  74.38%
gradient_radial2_mirror                         16999.49 11540.39  32.11%
gradient_radial2_clamp_hicolor                  17943.38 12501.71  30.33%
gradient_radial2_clamp                          17816.36 12492.04  29.88%
bitmaprect_FF_filter_trans                         47.81    10.98  77.03%
bitmaprect_FF_nofilter_trans                       47.79    10.91  77.18%
bitmaprect_FF_filter_identity                      47.74    10.89  77.18%
bitmaprect_FF_nofilter_identity                    47.83    10.89  77.24%
bitmap_4444_update_scale_rotate_bilerp            100.45    76.84  23.50%
bitmap_4444_update_volatile_scale_rotate_bilerp   100.80    76.70  23.91%
bitmap_4444_scale_rotate_bilerp                   100.43    77.18  23.15%
bitmap_4444_update_scale_bilerp                    79.00    49.03  37.93%
bitmap_4444_update_volatile_scale_bilerp           78.90    48.87  38.06%
bitmap_4444_scale_bilerp                           78.92    48.81  38.16%
bitmap_4444_update                                 42.19    11.53  72.68%
bitmap_4444_update_volatile                        42.28    11.49  72.82%
bitmap_a8                                          60.37    29.75  50.72%
bitmap_4444                                        42.19    11.52  72.69%

BUG=

Committed: http://code.google.com/p/skia/source/detail?r=13698

[qiankun, 2014-02-26 09:08:53]

PTAL, Thanks.

[qiankun, 2014-03-05 04:52:34]

On 2014/02/26 09:08:53, qiankun wrote:
> PTAL, Thanks.

ping.

[mtklein, 2014-03-06 17:14:17]

On 2014/03/05 04:52:34, qiankun wrote:
> On 2014/02/26 09:08:53, qiankun wrote:
> > PTAL, Thanks.
> 
> ping.

Thanks for reminding me.  This LGTM.  Correct clear code with a clear speed win!
  It makes me so happy.  :)

[qiankun, 2014-03-07 01:48:05]

The CQ bit was checked by qiankun.miao@intel.com

[commit-bot: I haz the power, 2014-03-07 01:48:12]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/qiankun.miao@intel.com/181293002/1

[commit-bot: I haz the power, 2014-03-07 03:25:35]

Change committed as 13698