Update SkOpts namespaces.

src/opts/SkOpts_sse41.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkOpts.h"
 
-#define SK_OPTS_NS sse41
+#define SK_OPTS_NS sk_sse41
 #include "SkBlurImageFilter_opts.h"
 
 namespace SkOpts {
     void Init_sse41() {
-        box_blur_xx = sse41::box_blur_xx;
-        box_blur_xy = sse41::box_blur_xy;
-        box_blur_yx = sse41::box_blur_yx;
+        box_blur_xx = sk_sse41::box_blur_xx;
+        box_blur_xy = sk_sse41::box_blur_xy;
+        box_blur_yx = sk_sse41::box_blur_yx;
     }
 }