go/importer: fix field/method package for binary importer
This is the equivalent of https://golang.org/cl/18549 for
the binary importer (which is usually not used because by
default the gc compiler produces the traditional textual
export format).
For #13898.
Change-Id: Idb6b515f2ee49e6d0362c71846994b0bd4dae8f7
Reviewed-on: https://go-review.googlesource.com/18598 Reviewed-by: Alan Donovan <adonovan@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>