Fixing usages of ptr_lib::shared_ptr

In certain cases, importing both std:: and ndn::ptr_lib namespaces
causes ambiguity for shared_ptr type.

Change-Id: Iddc02353e1615b2387277c56185a1dd873d54459
Basic structure parsing of NDN-TLV format

Change-Id: I3958dfe2bb11366ae5bab61247bf5dc339885fdd