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.

          <xsd:attribute name="Command" type="xsd:string" use="optional" default="make -C %(buildpath)s all BEREMIZSRC=%(src)s BEREMIZCFLAGS=%(cflags)s MD5=%(md5)s USE_BEREMIZ=1 FROM_BEREMIZ=1"/>