Cannot format zeek-7 IDs in global scope

zeek-7 changed the way global IDs are written from `GLOBAL::XYZ` to `::XYZ`. This syntax is not supported by e.g., `zeek-format`.

```zeek
type r: record { };

event zeek_init()
	{
	local x: ::r;
	}
```
```console
$ zeek-format foo.zeek
cannot parse line 5, col 9: ": :"
type r: record { };

event zeek_init()
        {
        local x : : : r;
        }
```