[Bug libstdc++/96416] address_of() is broken by static_assert in pointer_traits

[whatwasthataddress at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96416

--- Comment #2 from Zach Laine <whatwasthataddress at gmail dot com> ---
Fair enough.  [pointer.conversion] says that to_pointer(const Ptr& p) is
"pointer_­traits<Ptr>​::​to_­address(p) if that expression is well-formed (see
[pointer.traits.optmem]), otherwise to_­address(p.operator->())".  Do we then
have a spec bug?