gccgo: rejects valid imaginary literal

gccgo fails to compile the following program:

``` go
package A
var g=08i
```

```
go.go:2:8: error: expected ‘;’ or newline after top level declaration
```

Spec contains similar example:

```
011i  // == 11i
```

gcc version 6.0.0 20150702 (experimental) (GCC)
