cmd/compile: ensure ... rules have compatible aux and auxint types

Otherwise, just copying the aux and auxint fields doesn't make much sense.
(Although there's no bug - it just means it isn't typechecked correctly.)

Change-Id: I4e21ac67f0c7bfd04ed5af1713cd24bca08af092
Reviewed-on: https://go-review.googlesource.com/c/go/+/227962


Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>