Replaced TidyPointer with std::unique_ptr.

Replaced TidyPointer with std::unique_ptr.

LockingPointer is now a stand-alone class that is understood (and
documented) as a typical shared pointer with OpenSSL-friendly object
importing methods. Replaced its TidyPointer::reset() abuse with an
explicit resetWithoutLocking() method after reviewing that all such
calls needed no locking indeed.