Prototype MDP/0.2 implementation

There's no broker, just a basic worker and client.

This works with libmdp (http://github.com/zeromq/majordomo.git) tag "wire-protocol-0.2" with the following bug fix:

diff --git a/libmdp/include/mdp_common.h b/libmdp/include/mdp_common.h
index 7c91b7e..2aa1ceb 100644
--- a/libmdp/include/mdp_common.h
+++ b/libmdp/include/mdp_common.h
@@ -47,9 +47,9 @@ static char *mdpc_commands [] = {
 #define MDPW_READY          "\001"
 #define MDPW_REQUEST        "\002"
 #define MDPW_PARTIAL        "\003"
-#define MDPW_FINAL          "\003"
-#define MDPW_HEARTBEAT      "\004"
-#define MDPW_DISCONNECT     "\005"
+#define MDPW_FINAL          "\004"
+#define MDPW_HEARTBEAT      "\005"
+#define MDPW_DISCONNECT     "\006"

 static char *mdpw_commands [] = {
     NULL, "READY", "REQUEST", "PARTIAL", "FINAL", "HEARTBEAT", "DISCONNECT"