benchmark                  old ns/op     new ns/op     delta
    BenchmarkUnquoteEasy-4     188           79.5          -57.71%
    BenchmarkUnquoteHard-4     653           622           -4.75%

Fixes #23821

Change-Id: I1ebfab1b7f0248fd313de21396e0f8612076aa6d
Reviewed-on: https://go-review.googlesource.com/116755Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>