fixed plc_python.c to assure data coherancy from the PLC point of view. Also fix non work multiple python_eval FB instance case.
<xsd:element name="Xenomai">
<xsd:complexType>
%(toolchain_gcc)s
<xsd:attribute name="xeno_config" type="xsd:string" use="optional" default="/usr/xenomai/"/>
</xsd:complexType>
</xsd:element>