Perl_op_free still considered harmful

For some reason, if we free the former addop, we get a segfault later in
the runloop. Inline comment explains my current line of thinking, but
for now, we just don't free the addop.

  /* FIXME something still refers to the addop, so this segfaults.
   *       Maybe the parent and op_next fixups don't work?
   *       This would explain why the custom OP free hook never reaches
   *       the JIT OP. But execution of JIT OP seems to work just fine.
   *       That suggests that either I'm missing something fundamental, or the
   *       parent fixup is the part that's not right? */
Behold the first (uselessly) JIT'd function!

Same result as Perl. But most certainly a lot slower because we're just
replacing + with a function call. :)