Merge pull request #390 from hintjens/master

Added ZPL serialization to/from memory
Removed zprotocol as this is no use to anyone
Merge branch 'master' of github.com:zeromq/czmq
Merge pull request #391 from sappo/master

Removed zprotocol
Merge pull request #392 from hintjens/master

Problem: zmsg_dup returned NULL on empty msg
Added dup, fprint and print methods for zchunk
Merge pull request #393 from sappo/master

Added dup, fprint and print methods for zchunk
Slight tweak on _print
Simplified _dup