RFR: 8166220: Catalog API: JAXP XML Processor Support - add StAX test coverage

[Joe Wang]

Hi,

Please review an addition of StAX tests to the Catalog Support test set.

JBS: https://bugs.openjdk.java.net/browse/JDK-8166220
webrev: http://cr.openjdk.java.net/~joehw/jdk9/8166220/webrev/

Thanks,
Joe