Teach qdoc to understand typical C++ class functionality

There are some standard C++ class use cases that would be better documented with special wording automatically added to the \class comment than by documenting specific member functions.

e.g.: Qdoc could add some standard wording for a class that
can be copied (or not), and then we can get rid of the explicit
documentation for copy constructors and assignment operators. And let’s
document special cases where required.