Copter: change function definitions in guided to static
AC_WPNav: add set_spline_dest_and_vel function
Copter: add Guided_Spline mode
GCS_MAVLink: update MAV_FRAME enum
GCS_MAVLink: run generate.sh
Copter: handle SET_POSITION_TARGET mavlink messages
RC_Channel: replace long with int32_t
RC_Channel: add get_control_mid function
Copter: utilize get_control_mid for throttle calculations