Fix deadlock when indirectly calling PLCObject's evaluator() from twisted of wx event loops. Was freezing while transfer/start/stop through Wamp. Serialize all PLCObject's call to self.PythonRuntimeCall into the same PythonThread thread.

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<?xml version='1.0' encoding='utf-8'?>

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<ModbusRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema"/>