'Change POU Type To' becomes 'Duplicate as...', avoiding side effects of type change when POU is already instanciated. Also remove leftover returType tag in ex-function POUs, triggering exceptions at build time.
<xsd:element name="Xenomai">
<xsd:complexType>
%(toolchain_gcc)s
<xsd:attribute name="XenoConfig" type="xsd:string" use="optional" default="xeno-config"/>
</xsd:complexType>
</xsd:element>