Use a separate symbol for reflect metadata for types with Noalg set.

Fixes #17752.

Change-Id: Icb6cade7e3004fc4108f67df61105dc4085cd7e2
Reviewed-on: https://go-review.googlesource.com/32679Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>