Add comment to rigctl_parse.c

tests/rigctl_parse.c

@@ -3976,6 +3976,7 @@ declare_proto_rig(dump_state)
     // protocol 1 fields are "setting=value"
     // protocol 1 allows fields can be listed/processed in any order
     // protocol 1 fields can be multi-line -- just write the thing to allow for it
+    // backward compatible as new values will just generate warnings
     fprintf(fout, "vfo_ops=0x%"PRXll"\n", (unsigned long)rig->caps->vfo_ops);
     fprintf(fout, "done\n");