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

src/opts/SkBlurImage_opts_SSE2.h

Index: src/opts/SkBlurImage_opts_SSE2.h
diff --git a/src/opts/SkBlurImage_opts_SSE2.h b/src/opts/SkBlurImage_opts_SSE2.h
new file mode 100644
index 0000000000000000000000000000000000000000..4dd804aa1a5429ba4b8801e8a90e84bc357d326c
--- /dev/null
+++ b/src/opts/SkBlurImage_opts_SSE2.h
@@ -0,0 +1,12 @@
+/*
+ * Copyright 2013 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBlurImage_opts.h"
+
+bool SkBoxBlurGetPlatformProcs_SSE2(SkBoxBlurProc* boxBlurX,
+                                    SkBoxBlurProc* boxBlurY,
+                                    SkBoxBlurProc* boxBlurXY);