xml: differentiate between float32 and float64 for marshalSimple
xml: differentiate between float32 and float64 for marshalSimple

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/7235045

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang