SVGHMI : had to move the problem of wkaing up python thread from plc thread to platform specific code.
Since Xenomai's cobalt thread are definitely incompatible with normal posix python interpreter binary's thread, we must synchronize them with arcane rt_pipes (the only ones that really work cross domain) as already done in debug and python async eval blocks.

SVGHMI: change collect/send thread looping condition to fix infinite loop in some cases