Implement
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2468r2.html.
Primarily we now accept
template<typename T> struct CRTPBase { bool operator==(const T&) const; bool operator!=(const T&) const; }; struct CRTP : CRTPBase<CRTP> {}; bool cmp_crtp = CRTP() == CRTP(); bool cmp_crtp2 = CRTP() != CRTP();
NIT: for consistency with other diagnostics.