fix translation strings with multiple parameters


this fixes a lot of warnings given by msgmerge:

../PLCOpenEditor.py:196: warning: 'msgid' format string with unnamed arguments cannot be properly localized:
The translator cannot reorder the arguments.
Please consider using a format string with named arguments,

                  <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>