[Bug c++/58407] [C++11] Should warn about deprecated implicit generation of copy constructor/assignment

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58407

--- Comment #21 from Jonathan Wakely <redi at gcc dot gnu.org> ---
P.S. it's arguable whether abstract base classes should be copyable in the
first place:
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rc-copy-virtual
https://github.com/isocpp/CppCoreGuidelines/issues/1151