VARTest: fixed build with compass changes
Replay: fixed build of replay tool

changes to compass API
Copter: fixed typos in parameter markup
AC_AttControl: fixed typo in parameter description
GCS_Mavlink: moved some more mavlink functions to GCS_Common.cpp
Plane: update for new API
Copter: changes for more common mavlink code
Rover: changes for more common mavlink code
AntennaTracker: changes for more common mavlink code
GPS: exclude SIRF and NMEA on APM copter build

This only works for the centralised builder, the modified Arduino IDE
will still include the NMEA and SIRF drivers meaning it will require
approximately 4k additional flash which may push us over the limit on
the APM2.  Users will instead need to exclude other features to get
below the APM1/2 flash limit.
Copter: Acro balance fix