[util.smartptr.shared.cast] "Will eventually" is so sure

[zhihaoy]

There're four occurrences of "will eventually" in this section, for instance

[Note 1 : The seemingly equivalent expression shared_ptr<T>(static_cast<T*>(r.get())) will eventually
result in undefined behavior, attempting to delete the same object twice. --end note]

But what does it mean? If r.get() compares equal to nullptr, the program won't delete the same object twice. Moreover, in dynamic_pointer_cast's case, the program may run "correctly" sometimes if the users handled the case when dynamic_cast gives nullptr...

Suggestion:

- will eventually result in undefined behavior,
+ can result in undefined behavior,

[jwakely]

Yes, "can" seems better