Added 'NamedConstant' drag'n'drop in programs. It does create a simple variable with initial value and is usefull for drag'n'drop constants from extensions while keeping a name associated with constant
<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>