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