Raw pointer -> std::shared_ptr.
fix -Wextra warning.
C style cast -> C++ cast.
remove operator&&, operator||; "short-circuit evaluation".
fix member initialization list.
Add const member function.
Update use_hash()
T::Ptr -> const T::Ptr &
Add test_radix64.cpp
bugfix for find_decrypting_key().
bugfix Tag3.
Add PGPTest.
Update Makefile.