bump version 0.6.4
diff --git a/xxhash.h b/xxhash.h
index 5b14358..1313663 100644
--- a/xxhash.h
+++ b/xxhash.h
@@ -150,7 +150,7 @@
 ***************************************/
 #define XXH_VERSION_MAJOR    0
 #define XXH_VERSION_MINOR    6
-#define XXH_VERSION_RELEASE  3
+#define XXH_VERSION_RELEASE  4
 #define XXH_VERSION_NUMBER  (XXH_VERSION_MAJOR *100*100 + XXH_VERSION_MINOR *100 + XXH_VERSION_RELEASE)
 XXH_PUBLIC_API unsigned XXH_versionNumber (void);