Added support for non-zmq tcp client connections to router socket.

- Created a new option ZMQ_ROUTER_RAW_SOCK
    - Added new raw_encoder and raw_decoder to receive and send messages in raw form to remote client
    - Added test case file tests/test_raw_sock.cpp

    o To create a raw router sock set the ZMQ_ROUTER_RAW_SOCK option
    o ZMQ_MSGMORE flag is ignored for non-id messages
    o To terminate a remote connection send id message followed by zero length data message

src/options.cpp

@@ -55,6 +55,7 @@ zmq::options_t::options_t () :
     tcp_keepalive_intvl (-1),
     socket_id (0)
 {
+    raw_sock = false;
 }
 
 int zmq::options_t::setsockopt (int option_, const void *optval_,