This tries to make the visibility.h header clearer and better
structured. We don't actually need the ifdef for lockstep enabled or
disabled because that's now handled elsewhere.

visibility.h is included globally in PX4 via cmake compile flags.
It contains poisoning the exit() command which is used by gtest
to close the test application. Removing the flag for gtest compilation
fixes the compile error:
gtest.cc:4757:7: error: attempt to use poisoned "exit"

 - support range based for loops
 - add remove() method to remove a node
 - add clear() to empty entire list and delete nodes
 - add empty() helper

Instead of using the define __PX4_POSIX_SITL it makes more sense to have
a define just to determine if the lockstep scheduler should be used.

This makes sure lockstep is only built for SITL builds and fixes the
existing builds.

This integrates the lockstep_scheduler, so that the system time is set
by the mavlink HIL_SENSOR message.

This means that the speed factor is removed and the speed is entirely
given by the simulator.

These contains some rough changes trying to get SITL to speed up by a
SPEED_FACTOR.

This platform time code probably requires some more thought and refactor
but this gets a demo at 4x working.

This is another step to isolate time from the system.

This is a step towards isolating time from the system.

These leaks are not critical but the address-sanitizer complains.
And it's better programming practice anyway.

Signed-off-by: Lukas Woodtli <woodtli.lukas@gmail.com>

Generally exit() should not be used on Posix, because it exits the whole
program instead of only the task.

Just to make sure that it will never be used on NuttX. This is not an
architectural limitation, just a memory optimization, since we call
clearenv() on NuttX.

This moves the mavlink_log interface from ioctl to uORB and enables the
mavlink statusmessage output for Snapdragon. The API changes will lead
to changes in all modules that are using it.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

This brings in many of the changes from the PX4 fork on ATLFLight.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

This brings in many of the changes from the PX4 fork on ATLFLight.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

This brings in many of the changes from the PX4 fork on ATLFLight.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

Signed-off-by: Mark Charlebois <charlebm@gmail.com>