fix problem with clearing non-empty location field after changing type of config variable
introduced by cd9db17 ("clear variable location cell in variable
panel, if variable class or type changed").
Closes #26
<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>