mboxctl: Implement mboxctl to facilitate dbus control of the daemon

The daemon can now be controlled by issuing commands over dbus.
Implement a mailbox control program to facilitate communication
with the daemon over dbus.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Change-Id: I2a11f187268d28ce92d3c2592e0021e1ba5588b4
diff --git a/dbus.h b/dbus.h
index 4e5aa04..aa520c2 100644
--- a/dbus.h
+++ b/dbus.h
@@ -44,6 +44,7 @@
 #define E_DBUS_INVAL		0x02 /* Invalid Command */
 #define E_DBUS_REJECTED		0x03 /* Daemon Rejected Request */
 #define E_DBUS_HARDWARE		0x04 /* BMC Hardware Error */
+#define E_DBUS_NO_MEM		0x05 /* Failed Memory Allocation */
 
 /* Response Args */
 /* Status */