Previous behavior was undocumented and inconsistent. Now it is documented
and consistent and measures the input size, since that makes more sense
when talking about %q and %x. For %s the change has no effect.
Fixes#8151.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/144540044
Converting an integer to an interface{} allocates as of CL 130240043.
Fixes#8617.
LGTM=r
R=r
CC=golang-codereviews, khr
https://golang.org/cl/141700043
With new interface allocation rules, the old counts were wrong and
so was the commentary.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/142760044