Use more conventional field order in Mutation

include/VersionedMap.h

@@ -60,8 +60,8 @@ struct __attribute__((__visibility__("default"))) VersionedMap {
   /** Mutations are bitwise-lexicographically ordered by param1. */
   struct Mutation {
     const uint8_t *param1;
-    const uint8_t *param2;
     int param1Len;
+    const uint8_t *param2;
     int param2Len;
     MutationType type;
   };