AP_Airspeed: fixed example build
AP_InertialSensor: fixed example builds
AP_Math: fixed example build
AP_Notify: fixed example build
Plane: prepare for 2.78 release
Copter: firmware to AC3.1.2-rc1
Copter: remove unused compat.pde entries
updates to 2.78

git fetch upstream
git merge upstream/master

Merge remote-tracking branch 'upstream/master'