Add define map

[redboltz]

No description provided.

[redboltz]

When you use MSGPACK_DEFINE_MAP and MSGPACK_BASE_MAP, the members of class are serialized as MAP. Converting and creating msgpack::with_zone are also supported.

When you use MSGPACK_DEFINE_ARRAY and MSGPACK_BASE_ARRAY, the members are serialized as array. MSGPACK_DEFINE and MSGPACK_BASE is aliases of MSGPACK_DEFINE_ARRAY and MSGPACK_BASE_ARRAY by default. If you define MSGPACK_USE_DEFINE_MAP, they become the aliases of MSGPACK_DEFINE_MAP and MSGPACK_BASE_MAP.

The keys of the map are variables name. When you use MSGPACK_BASE_MAP, the key of the map is the name of the base class.

You can serialize and deserialize without an order restriction as follows:
https://github.com/msgpack/msgpack-c/pull/306/files#diff-aac96dea4ddf2c5c29096d6d6e5b0874R433

In order to implement this functionality, I use Boost.Preprocessor. So if you want to use the MSGPACK_DEFINE_MAP and MSGPACK_BASE_MAP, you need to define MSGPACK_USE_BOOST. If you don't, you don't need Boost Libraries and it is a default setting.