Convert yyerrors into Fatals.
Remove the goto.
Move variable declaration closer to use.
Unify printing strings a bit.
Convert an int param into a bool.

Passes toolstash-check. No compiler performance impact.

Change-Id: I9017681417b785cf8693d18b124ac4f1ff37f2b5
Reviewed-on: https://go-review.googlesource.com/39170
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>