pushedio.bin and importpkg are both non-nil iff we're parsing an
package's export data, so "pushedio.bin == nil" and "importpkg == nil"
are equivalent tests.

Change-Id: I571ee908fef867117ef72c5da1eb24fe9b3fd12d
Reviewed-on: https://go-review.googlesource.com/19751Reviewed-by: Robert Griesemer <gri@golang.org>