Xenomai runtime: report and mitigate when PLC cycle overruns.

Side effect :
_Log* macro was changed in plc_Xenomai_main.c,
and fixed in plc_Linux_main.c

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot URI_location="LOCAL://">
  <TargetType/>
  <Libraries Enable_SVGHMI_Library="true"/>
</BeremizRoot>