SSE2 implementation of S32_D565_Opaque

SSE2 implementation of S32_D565_Opaque

Benchmarks hitting this path can benfit from this patch.
Here are the data:
                                    before      after
        gradient_radial2_mirror   10885.52   10849.48   0.33%
 gradient_radial2_clamp_hicolor   11819.69   11644.83   1.48%
         gradient_radial2_clamp   11816.10   11649.91   1.41%
     bitmaprect_FF_filter_trans       6.27       4.88  22.17%
   bitmaprect_FF_nofilter_trans       6.27       4.88  22.17%
  bitmaprect_FF_filter_identity       6.31       4.86  22.98%
bitmaprect_FF_nofilter_identity       6.25       4.86  22.24%
             bitmap_4444_update       6.26       5.05  19.33%
    bitmap_4444_update_volatile       6.21       5.06  18.52%
                    bitmap_4444       6.22       5.06  18.65%

BUG=

Committed: http://code.google.com/p/skia/source/detail?r=13556

[qiankun, 2014-02-19 09:10:41]

PTAL, thanks:)

[mtklein, 2014-02-21 17:11:09]

On 2014/02/19 09:10:41, qiankun wrote:
> PTAL, thanks:)

lgtm

Things sure are easy when you don't need to read dst!

[qiankun, 2014-02-24 04:09:49]

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

[commit-bot: I haz the power, 2014-02-24 04:10:08]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/qiankun.miao@intel.com/172083003/1

[commit-bot: I haz the power, 2014-02-24 04:23:41]

Change committed as 13556