XSModels.  This also cleans up handling in the
parser classes by eliminating the need to tell
the grammar pool that schema compoments need to be produced.
Thanks to David Cargill.


git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@175431 13f79535-47bb-0310-9956-ffa450edef68