Bug 1300124 - make MurmurHash3.cpp compile with clang-cl; r=bkelly

Including headers inside anonymous namespaces, especially standard headers,
is super-unusual; let's just move the header to the toplevel instead.

MozReview-Commit-ID: CNykWQA5ndY

--HG--
extra : rebase_source : e5011cd18c1a0d31d4ae15ae3f3697eafac5f575

dom/canvas/MurmurHash3.cpp

@@ -8,6 +8,7 @@
 // non-native version will be less than optimal.
 
 #include "MurmurHash3.h"
+#include <stdlib.h>
 
 namespace {
 
@@ -20,8 +21,6 @@ namespace {
 
 #define FORCE_INLINE	__forceinline
 
-#include <stdlib.h>
-
 #define ROTL32(x,y)	_rotl(x,y)
 #define ROTL64(x,y)	_rotl64(x,y)