Revert "cmd/stringer: reject Go 1.8 type aliases"

This reverts commit 9a286cdc334bcda1296aaa1c8cc85c2d5d64dac7.

Reason for revert: go1.8 code in a go1.7 file.

Change-Id: I5465820c60197f4288243d1b15b1be20531b923d
Reviewed-on: https://go-review.googlesource.com/32733
Reviewed-by: Alan Donovan <adonovan@google.com>
2 files changed