Update common.xml

Proposal to add direct battery charge and energy consumption reporting in addition or instead of the current percentage of battery.  

The problem with the battery percentage is that the on-board system in most cases does not natively know the size of the energy storage and relies on the (possibly) configured battery capacity value.  In case of changing the battery on the field there may be different battery size or there may be a different type of power source on board. In any case, the percentage value is secondary information and dependent on a pre-configured capacity value, which may or may not be correct or relevant.  

If the on-board system has capability to report any consumption numbers, it almost certainly is measuring current and voltage samples.  These are primary information available to be reported and should be reported.

Possibly it could make sense to split message 147 to two separate messages: 1) multi-cell battery individual cell voltage reporting 2) total voltage & current readings and derivatives.
1. Fixed field closing tag.  2. Increased current and energy consumption field sizes.

Field size increase to accommodate kilowatt-size power trains and long missions. A more airlink economical option would be to use one scalar byte for both of the consumption fields.  However, not sure if the savings would carry their weight in added complexity.
Permits external m_mavlink_status array.
Added a message encoding function that accepts a channel.

In the C-API, just like there are the `mavlink_msg_msgname_pack` and `mavlink_msg_msgname_pack_chan` functions, there should be  `mavlink_msg_msgname_encode` and `mavlink_msg_msgname_encode_chan` functions, as not all messages are sent over the MAVLINK_COMM_0 channel and need the appropriate sequence number set.
Add AutoQuad to CMakeLists.txt
Merge branch 'master' of https://github.com/mavlink/mavlink into upstream
Add custom mode enum to AutoQuad definitions.
Merge pull request #123 from AutoQuad/upstream

Add some AutoQuad custom definitions and add autoquad.xml to CMakeLists
Merge pull request #120 from dimasad/master

Fixes in external rx buffer logic and adds possibility for external rx status
Merge pull request #121 from dimasad/msg_encode_chan

Added a message encoding function that accepts a channel.
mavwp: added support functions for fence editing
pymavlink: added add_latlonalt() for waypoint map editing
APM: changed SIMSTATE to use int32_t lat/lon

this allows us to test the full accuracy of GPS drivers. Note that
SIMSTATE is only used by mavproxy at the moment, so changing this
doesn't break anything else
mavutil: changed mavlink_connection() to support open retries on TCP

this avoids race conditions in SITL startup
mavextra: added airspeed_ratio() and improved gps velocity
pymavlink: fixed generator to run from installed package
messages: added MAV_CMD_DO_SET_ROI

this is used by ArduCopter
pymavlink: update version
ardupilotmega: added AIRSPEED_AUTOCAL message

used for debugging airspeed calibration EKF
pymavlink: fixed mag_heading() calculation