Contribute new testcase Interface-6B

Please find attached a patch file containing a new testcase, Interface-6B,
which I would like to contribute to the WSDL 2.0 assertion test suite.

This testcase violates interface extension assertion Interface-1009 in a
similar way to the existing test Interface-3B. However, this new testcase
includes operations, faults and bindings, so it provides a more thorough
test in that a WSDL 2.0 processor must not only detect that the assertion
has been violated, but it must also handle the circular reference correctly
if it attempts to process the operations, faults and binding to avoid an
infinite loop.  This testcase is in response to a comment made by Jacek on
Apache Woden JIRA  http://issues.apache.org/jira/browse/WODEN-159

regards,
John Kaputin