This ensures that importpath symbols are treated like other type data
and end up in the same section under all build modes.

Fixes: go test -buildmode=pie reflect

Change-Id: Ibb8348648e8dcc850f2424d206990a06090ce4c6
Reviewed-on: https://go-review.googlesource.com/22081
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>