Make sure types in ABI are standard layout

include/VersionedMap.h

@@ -104,7 +104,12 @@ struct VersionedMap {
     Iterator(Iterator &&) noexcept;
     Iterator &operator=(Iterator &&) noexcept;
 
-    struct VersionedMutation : Mutation {
+    struct VersionedMutation {
+      const uint8_t *param1;
+      const uint8_t *param2;
+      int param1Len;
+      int param2Len;
+      MutationType type;
       int64_t version;
     };
 
@@ -122,7 +127,7 @@ struct VersionedMap {
     Iterator operator--(int);
 
     using difference_type = ptrdiff_t;
-    using value_type = Mutation;
+    using value_type = VersionedMutation;
 
     bool operator==(const Iterator &) const;
     bool operator!=(const Iterator &) const;