SITL: fixed SITL for example sketches

cope with no SITL object
AP_HAL: fixed printf example build
AP_HAL: addex UART_test example sketch
AP_HAL: fixed RCOutput example
AP_HAL: added RCInput example sketch
RC_Channel: update example sketch to copy input to output
DataFlash: fixed example sketch build
GCS_MAVLink: re-generate with updated upstream mavlink
AP_Mission: ensure location options are zero at start of mavlink conversion
Plane: prevent a change altitude command from causing a sudden descent

when a change altitude command comes in while a large glide slope
altitude change is present we could end up using the old glide slope
with the new altitude. This resets the altitude offset, causing a
direct altitude change
Plane: re-enable CLI on non-APM1/APM2 boards