Improving the wording of std::shared_ptr

Section 20.6.6.2 [util.smartptr.shared], paragraph 1, talks about the class template shared_ptr storing a pointer, but does not introduce explicit the pointer owned by the shared pointer (with the corresponding object of some type Y that is being owned). This makes it hard for the reader to realize that this is different from the pointer stored by this same shared pointer (the address of the object of type T that is being pointed to). This difference exists because of pointer conversions, but is