cmd/cgo: remove duplicate mangle definition

Change-Id: I0f8c695146b39cff72ca2374f861f3e9f72b0f77
Reviewed-on: https://go-review.googlesource.com/41314Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/cgo/out.go

@@ -185,7 +185,7 @@ func (p *Package) writeDefs() {
 	for _, key := range nameKeys(p.Name) {
 		n := p.Name[key]
 		if n.Const != "" {
-			fmt.Fprintf(fgo2, "const _C%s_%s = %s\n", n.Kind, n.Go, n.Const)
+			fmt.Fprintf(fgo2, "const %s = %s\n", n.Mangle, n.Const)
 		}
 	}
 	fmt.Fprintf(fgo2, "\n")