test: match gccgo error messages for label.go and label1.go.
label.go:30:1: error: label ‘L6’ already defined
label.go:28:1: note: previous definition of ‘L6’ was here
label.go:23:1: error: label ‘L4’ defined and not used
label.go:52:2: error: label ‘defalt’ defined and not used
label.go:17:1: error: label ‘L2’ defined and not used
label.go:26:1: error: label ‘L5’ defined and not used
label.go:20:1: error: label ‘L3’ defined and not used
label.go:14:1: error: label ‘L1’ defined and not used
label1.go:32:13: error: invalid continue label ‘L2’
label1.go:44:13: error: invalid continue label ‘L3’
label1.go:52:10: error: invalid break label ‘L4’
label1.go:55:13: error: invalid continue label ‘L4’
label1.go:65:9: error: invalid break label ‘L5’
label1.go:68:12: error: invalid continue label ‘L5’
label1.go:76:10: error: invalid break label ‘L1’
label1.go:79:13: error: invalid continue label ‘L1’
R=rsc
CC=golang-dev
https://golang.org/cl/
4275078