SSE2 implementation of RGBA box blurs. This yields ~2X perf improvement on

src/opts/SkBlurImage_opts_none.cpp

Index: src/opts/SkBlurImage_opts_none.cpp
diff --git a/src/opts/SkMorphology_opts_none.cpp b/src/opts/SkBlurImage_opts_none.cpp
similarity index 58%
copy from src/opts/SkMorphology_opts_none.cpp
copy to src/opts/SkBlurImage_opts_none.cpp
index 66d58ba571fe18208ebf90fd301884ad19f42c91..e31dccd0893ed5e46222668cf02925a7f80c2859 100644
--- a/src/opts/SkMorphology_opts_none.cpp
+++ b/src/opts/SkBlurImage_opts_none.cpp
@@ -5,8 +5,8 @@
  * found in the LICENSE file.
  */
 
-#include "SkMorphology_opts.h"
+#include "SkBlurImage_opts.h"
 
-SkMorphologyProc SkMorphologyGetPlatformProc(SkMorphologyProcType) {
+SkBoxBlurProc SkBoxBlurGetPlatformProc(SkBlurDirection srcDirection, SkBlurDirection dstDirection) {
     return NULL;
 }