SVGHMI: rework Jump widget to cope with Enable Expressions.
Relative jumps are not disabled implicitely anymore when pointed HMI_NODE is 0.
Also, "activable()" implementation was enhanced to make it optional.
<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>