AP_ServoRelayEvents: fixed disabling repeated events on set_servo()
RC_Channel: simplify the setup of aux channels

avoid the nasty mess of #if lines, as the info is in the constructor
anyway
Plane: use new RC_Channels API
Copter: use new RC_Channels API
Rover: use new RC_Channels API
RC_Channel: added flaperon1 and flaperon2 function outputs
Plane: added flaperon support

this adds FLAPERON_OUTPUT and FLAP_IN_CHANNEL to allow both manual
and auto flap control for both normal flaps and flaperons
Plane: allow FLAP_IN_CHANNEL to control k_flap and k_flap_auto too
RC_Channel: added disable_aux_channel()

this will be used by copter to ensure motor channels are not enabled
for aux functions
Copter: ensure that motor channels cannot be used for auxillary functions

disable RC_Channel_aux channels that are used for motors. This perhaps
should be done by the AP_Motors library, but for now this is simpler