Add support for system-out / system-err at <testsuite/> level.

Testsuite can have system-out / system-err per junit.xsd.

...
<xs:element name="testsuite">
    <xs:complexType>
        <xs:sequence>
            <xs:element ref="properties" minOccurs="0" maxOccurs="1"/>
            <xs:element ref="testcase" minOccurs="0" maxOccurs="unbounded"/>
            <xs:element ref="system-out" minOccurs="0" maxOccurs="1"/>
            <xs:element ref="system-err" minOccurs="0" maxOccurs="1"/>
        </xs:sequence>
        <xs:attribute name="name" type="xs:string" use="required"/>
        <xs:attribute name="tests" type="xs:string" use="required"/>
        <xs:attribute name="failures" type="xs:string" use="optional"/>
        <xs:attribute name="errors" type="xs:string" use="optional"/>
        <xs:attribute name="time" type="xs:string" use="optional"/>
        <xs:attribute name="disabled" type="xs:string" use="optional"/>
        <xs:attribute name="skipped" type="xs:string" use="optional"/>
        <xs:attribute name="timestamp" type="xs:string" use="optional"/>
        <xs:attribute name="hostname" type="xs:string" use="optional"/>
        <xs:attribute name="id" type="xs:string" use="optional"/>
        <xs:attribute name="package" type="xs:string" use="optional"/>
    </xs:complexType>
</xs:element>
...
Add Damien Nozay to authors