Use sse4.2 CRC32 instructions to hash when available.

src/opts/SkOpts_sse42.cpp

Index: src/opts/SkOpts_sse42.cpp
diff --git a/src/opts/SkOpts_avx.cpp b/src/opts/SkOpts_sse42.cpp
similarity index 61%
copy from src/opts/SkOpts_avx.cpp
copy to src/opts/SkOpts_sse42.cpp
index b5df2b69f0ce3dbc2a6a1b56c14c0747ef88a98b..18831821920cf16e8e3d88e6d90b46756f41dae2 100644
--- a/src/opts/SkOpts_avx.cpp
+++ b/src/opts/SkOpts_sse42.cpp
@@ -7,8 +7,12 @@
 
 #include "SkOpts.h"
 
-#define SK_OPTS_NS avx
+#define SK_OPTS_NS sse42
+#include "SkChecksum_opts.h"
 
 namespace SkOpts {
-    void Init_avx() { }
+    void Init_sse42() {
+        hash_fn = sse42::hash_fn;
+    }
 }
+