test: match gccgo error messages for cmp6.go
test: match gccgo error messages for cmp6.go

cmp6.go:28:9: error: incompatible types in binary expression
cmp6.go:29:9: error: incompatible types in binary expression
cmp6.go:40:9: error: incompatible types in binary expression
cmp6.go:41:9: error: incompatible types in binary expression
cmp6.go:48:9: error: expected integer, floating, complex, string, pointer, boolean, interface, slice, map, channel, or function type

R=rsc, r2
CC=golang-dev
http://codereview.appspot.com/4281071

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang