Useful for 4-in-1 ESCs such as the Hobbywing XRotor Micro 40A 4in1
where the FC can be directly plugged on top.

- Catch the case where the case where the driver gets stuck because nothing is received by +SBDRB
- Add a mutex for the rx buffer
- Stop the standby loop if a mode change is already scheduled

- Move publishing the telemetry status from the IridiumSBD driver to the mavlink instance
- In the commander use the iridiumsbd_status message for heartbeat in case of a high latency link
- Move positive acknowledge to the mavlink instance
- Add a failed acknowledge in the commander if no high latency link exists

* Add return to land to mission

This method uses the planned mission for rtl. If a landing sequence
is present it will continue the mission and land. If not it will
fly back the mission and loiter/land at the home position.

These are the default github examples and need to be customized.

https://blog.github.com/2018-05-02-issue-template-improvements/

Reduces FLASH usage by about 4KB

Command to replace:
for i in *.mix; do sed -r -i '/O: +10000 +10000 +0 +-10000 +10000/d' $i; done

These hard coded paths assume all Nuttx targets are ARMv7-M targets. Updating them to use ${CONFIG_ARCH} and ${CONFIG_ARCH_FAMILY} instead allows for the architecture defined by the incoming Nuttx defconfig to be correctly targeted.

Signed-off-by: Roman <bapstroman@gmail.com>

- just use external mag, if they run together the sensor_mag_0 topic gets
corrupted even though they publish on different instances
- added sleep at two places, they resolve weird boot problems like params
not being read correctly...

Signed-off-by: Roman <bapstroman@gmail.com>

Signed-off-by: Roman <bapstroman@gmail.com>

Signed-off-by: Roman <bapstroman@gmail.com>

    - ecl in PX4/Firmware (9e6449570a58587b7dd0f4919ea9d6f0a52f5239): https://github.com/PX4/ecl/commit/cb63f16d48d56de7ab407d2f78317ddfabd23747
    - ecl current upstream: https://github.com/PX4/ecl/commit/50631e5d98e61093e85e798570503e4055e887ca
    - Changes: https://github.com/PX4/ecl/compare/cb63f16d48d56de7ab407d2f78317ddfabd23747...50631e5d98e61093e85e798570503e4055e887ca

    50631e5 2018-05-21 Daniel Agar - geo remove use of DBL_EPSILON

    - sitl_gazebo in PX4/Firmware (ac55a0de): https://github.com/PX4/sitl_gazebo/commit/cd91ef411aff947f234eb829479e6242d9fabcf7
    - sitl_gazebo current upstream: https://github.com/PX4/sitl_gazebo/commit/651ca351fd1030870b42528db17e4fe2816d46e5
    - Changes: https://github.com/PX4/sitl_gazebo/compare/cd91ef411aff947f234eb829479e6242d9fabcf7...651ca351fd1030870b42528db17e4fe2816d46e5

    651ca35 2018-05-18 Elia Tarasov - fix vision quaternion transformation

    - DriverFramework in PX4/Firmware (381d3ccd577484a57e555ec9ad6166249d590140): https://github.com/PX4/DriverFramework/commit/e06222dd151e2f92476762e483915df5bd67929d
    - DriverFramework current upstream: https://github.com/PX4/DriverFramework/commit/410e9fc4e78da91030e9d535a7f8e023a9ddd1f4
    - Changes: https://github.com/PX4/DriverFramework/compare/e06222dd151e2f92476762e483915df5bd67929d...410e9fc4e78da91030e9d535a7f8e023a9ddd1f4

    410e9fc 2018-05-18 Roman - mpu9250: set internal gyro dlpf frequency to 92 Hz