Nicer swaps, loops (removed tmp variables). Use of bool instead of int.

This change passes go build -toolexec 'toolstash -cmp' -a std.

Change-Id: I541904c74b57297848decc51a8a4913a8eca4af3
Reviewed-on: https://go-review.googlesource.com/14316
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>