Adding enum field to int types that are linked with an enum
pymavlink: added distance_gps2() function
pymavlink: recognise an antenna tracker
pymavlink: allow calculation of EKF position in mavextra
mavgen: add _send_buf() varient of convenience MAVLink send() function

this varient reduces stack space usage for replying to an incoming
MAVLink message by reusing the incoming message buffer
message_definitions: added MAV_TYPE for onboard (companion) controller
pymavlink: allow conditionals on parameters in DF logs
pymavlink: reduced CPU usage on failed reads looping
pymavlink: fixed time handling in mavgraph
common.xml: added RC_CHANNELS message with 18 channels

see discussion on drones-discuss with Lorenz
pymavlink: raise version
pymavlink: fixed sleep time in blocking recv handling
pymavlink: fixed sequence number handling

this is what caused mavtester to lose packets
pymavlink: raise version
ardupilotmega: added MAV_CMD_DO_FENCE_ENABLE
common: added MAV_SYS_STATUS_GEOFENCE to MAV_STATUS_SENSOR field
XML: added MAV_CMD_NAV_SPLINE_WAYPOINT

This is used to create a spline path waypoint
pymavlink: raise version
pymavlink: draw spline waypoints on map
common.xml: added SERIAL_CONTROL message

this message allows for control of a serial device on a remote
node. This can be used to (for example) update the firmware on a 3DR
air radio by connecting to a Pixhawk over USB.