This example demonstrates automatic switches back and forth hard real timer.
Whenever you ask for a Linux service while being in hard real time LXRT sends
you to soft real time and then calls Linux. Your process will go back to hard
real time at the next LXRT call. In between you are in the hand of Linux.
To use it you must enable the macro ALLOW_SYSW in lxrt.c

Since it avoids crashes it should be usefull during testing.

Test.c shows it by continuously suspending itself on rt_sleep. Its use has
allowed to verify the reliability of the mechanism for switching back and forth
from hard to soft and viceversa.
