cmd/compile: compiles incorrect program

``` go
package e
const (
    A=false
```

```
$ go tool compile -oldparser /tmp/test.go
/tmp/test.go:18: syntax error: unexpected EOF, expecting )
$ go tool compile /tmp/test.go
```

go version devel +25a28da Sun Nov 15 23:41:28 2015 +0000 linux/amd64
