beremiz

check_source.sh: fix sed error: -e expression #1, char 25: Invalid range end

Warning happen only if old sed (4.4) is used.
<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>