cmd/compile: parsing problem

old/new parser disagree on error message for the following program:

``` go
package n
{
```

```
$ go tool compile a.go
syntax error: non-declaration statement outside function body
$ go tool compile -oldparser a.go
syntax error: unexpected semicolon or newline before {
```

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