msgpack::unpacked is a typedef of the msgpack::object_handle.
I recommend using msgpack::object_handle. It can be used not only
holding unpacked msgpack objects but also msgpack::objects that are
created by any types.
Replaced unpack() APIs in test codes and examples. They used to use old
APIs.
Replaced boost/ with msgpack/ and BOOST with MSGPACK in Boost.Preprocessor files.
Renamed existing macron in versioning.hpp to avoid confict with MSGPACK_PP_*.
Removed MSGPACK_USE_BOOST requirement from MSGPACK_DEFINE_MAP.