Undo pull request #16

Pull request #16 should not have been merged, as it only updated a miniscule part of the ZeroMQ API and left the rest unchanged and inconsistent. Prior to this change, this repository contained headers and bindings for ZeroMQ 4.0.5, which is the latest *stable* release of ZeroMQ. (Note the version numbers on [line 35 in zmq.d](https://github.com/D-Programming-Deimos/ZeroMQ/blob/master/deimos/zmq/zmq.d#L35).) In this version, the size of `zmq_msg_t` is 32 bytes.

The size of `zmq_msg_t` changed to 48 bytes in ZeroMQ 4.1, which currently has "release candidate" status. Personally, I don't think deimos.zmq needs to support a non-stable ZeroMQ version, but if it does, then it should be done properly. The whole 4.1 C headers should be copied, and the entire D binding should be updated correspondingly.