undeclared name: efaceOf on Go 1.7

I try this code:

``` go
// main.go
package main

func DoesNotError() error {
        return nil
}

func main() {
        DoesNotError()
}
```

**Expect**
It should work fine.

**Actual**
Throws an error below:

```
$ gopherjs build main.go
../../../../go/go/src/runtime/error.go:69:7: undeclared name: efaceOf
```
