stabilize_hil: Use Ivory-based stabilizer.

- The generated C code is checked in for now.  Run "build.sh" in
  the "ivory" subdirectory to regenerate it.
- Fix typo in motor output causing incorrect servo values.
- Break out stabilization code into a separate C module.
- Re-align with source tree layout changes.
Add MAVProxy logfiles to .gitignore.
libsmaccpilot: Motor output fixes.

- Give back "apmotors_mutex" after retrieving servo data.
- Initialize "apmotors_wrapper" from "motorsoutput_init" rather than
  the motors task so the main loop cannot run before all mutexes are
  created.
libsmaccmpilot: Fix RC input channels for roll and yaw.

- It looks like this fix got lost during the reorganzation.
stabilize_hil: Fix HIL servo output via MAVLink.

- Remove duplicate "servos_result" structure.
- Read servos from motors in main loop.
- Output servos to GCS in main loop.