[Bug c++/91618] template-id required to friend a function template, even for a qualified-id

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91618

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
>From Bug 88725

gcc fails to deduce that the friend declaration refers to ::func<int> in the
below

```
template <typename T>
void func(T);

class Cls {
    friend void ::func(int);
};
```

Rejecting with 

```
error: 'void func(int)' should have been declared inside '::'
     friend void ::func(int);
                           ^
```

I believe this should be allowed by [temp.friend]/1.3:
http://eel.is/c++draft/temp.friend#1.3

see discussion here: https://stackoverflow.com/q/54055575/1013719