cmd/gc: merge casep and casee labels
cmd/gc: merge casep and casee labels

The code inside the casee and casep labels can perfectly be merged since
they essentially do the same. The character to be stored where cp points is
just the character contained by the c variable.

R=golang-dev, dave, rsc
CC=golang-dev
https://codereview.appspot.com/6845112

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

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