this change removes the state field from the lexer,
because it's only used by the run method and can be
replaced with a local variable

Change-Id: Ib7a90ab6e9a894716cba2c7d9ed71bf2ad1240c0
Reviewed-on: https://go-review.googlesource.com/47338Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>