[Bug c++/88672] friend class template declaration in a class template is ignored

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88672

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Also, https://gcc.gnu.org/bugs very clearly says we need the testcase in
bugzilla, and not just a URL to some other site.