new C14N api method to allow to enforce default namespace propagation to the c14n-ized root element.
This allows us to do the STRTransform in WSS4j without string manipulation after canonicalization.


git-svn-id: https://svn.apache.org/repos/asf/santuario/xml-security-java/trunk@1460135 13f79535-47bb-0310-9956-ffa450edef68