[phobos] std.msgpack

[Masahiro Nakagawa]

A month ago, I announced msgpack4d at D.announce.
After that, I fixed bugs and improved some features.

Additional list:
- real support (suggested by Lars)
- enum support (reported by Hoshi)
- direct-conversion deserializer (suggested by Michel).
- DeflateFilter (originally DeflationBuffer)

A community review settled down.
I think current status is practicable quality.
So, I would like to add this to Phobos.

Do you see any problems?


Masahiro