Add back pwm out sim module so HITL simulation works again.

    - ecl in PX4/Firmware (aed3d80d5982f37e8353d6d07e29c79a9260b086): https://github.com/PX4/ecl/commit/f95cd4b3584d029c35b288a39180ddf25b2dd004
    - ecl current upstream: https://github.com/PX4/ecl/commit/c4492b17c1d7bb9b74011efa9890452b091421e8
    - Changes: https://github.com/PX4/ecl/compare/f95cd4b3584d029c35b288a39180ddf25b2dd004...c4492b17c1d7bb9b74011efa9890452b091421e8

    c4492b1 2019-04-09 Martina - do not reset yaw if vehicle on ground
14227ea 2019-04-08 Julian Oes - CMakeLists.txt: fix cmake warning
f97f0b6 2019-03-30 Paul Riseborough - EKF: Remove unnecessary code
43b5e26 2019-03-02 Paul Riseborough - EKF: Fix bug causing continual yaw reset when EKF2_MAG_TYPE = 2

With 24 MHz accesses to the SD card were unreliable. And the chance of
failure recently got worse, so that logging became impossible.

 - needed for code coverage of python scripts

- platform is optional and matters for Visual Studio builds
- `ver` command shows the windows version
and was just my first CI test

    - mavlink v2.0 in PX4/Firmware (88f2a685): https://github.com/mavlink/c_library_v2/commit/171c83700c6318af9ffb4a7ee733567b55a14543
    - mavlink v2.0 current upstream: https://github.com/mavlink/c_library_v2/commit/c6ab0459343c78a6a424514b5f64fa65d8cc0cf8
    - Changes: https://github.com/mavlink/c_library_v2/compare/171c83700c6318af9ffb4a7ee733567b55a14543...c6ab0459343c78a6a424514b5f64fa65d8cc0cf8

This should fix the macOS build.

When using QGC and/or the Dronecode SDK it was possible to get in a
state where the two mavlink instances were both publishing their last
heartbeat_time and cause commander to consistently toggle between
data link lost and regained. With this fix, we only ever look at the
very last heartbeat time and therefore seem to avoid this issue.

This prevents a warning message being printed to SITL users because the
UAVCAN_ENABLE param does not exist.

With this change the param SDLOG_MODE can be used for SITL as well.

loiter mode since it's the failsafe mode

instance protected

updateAvoidanceSetpoints->updateAvoidanceDesiredSetpoints

to check progress

waypoints in FlightTasks. In obstacle avoidace library reset desired
avoidance waypoints after publication