O930-031
XSD files with no namespace information cannot be mixed into the
same XML_Grammar, or they will conflict with each other. The
solution is therefore to preload each of them into its own XML_Grammar,
and then let the validating parser chose that grammar dynamically
by overriding the new primitive operation Parse_Grammar.
Change-Id: I337d09259c6b2b18d9b91b4ded847f7f8dcd6eab
