strconv: fix documentation for CanBackquote.
Space is not a control character.

Fixes issue 8571.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://codereview.appspot.com/137380043
fmt: fix allocation test
With new interface allocation rules, the old counts were wrong and
so was the commentary.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://codereview.appspot.com/142760044