SITL (copter.exe) will no longer connect to Mission Planner.

#### Issue details
SITL (copter.exe) appears to have become broken overnight.
Restarted the SITL sim this morning and neither Mission Planner nor MavProxy will connect to it (both report no heartbeat packets).

The SITL console window (MSDOS prompt box) shows:
Invalid Param RC7_OPTION in defaults file
AP_PARAM: invalid param in defaults file
(I'm not sure if this is relevant but I don't remember having seen these errors previously)

#### Version
Whatever version was automatically downloaded on 1st August 2018

#### Platform
[ ] All
[ ] AntennaTracker
[ * ] Copter (SITL - copter.exe)
[ ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
N/A

#### Hardware type
N/A

Start by reproducing the failure with copter.exe and attempt connections from Mission Planner and MavProxy, recording whether heartbeat packets appear. Inspect the SITL console output for the RC7_OPTION and invalid-parameter errors; done means both clients connect successfully without the reported heartbeat or defaults-file errors.

Written by the indexing model from the issue text.