RFR[8183266] - [TESTBUG]Add test to cover XPathEvaluationResult.XPathResultType.getQNameType method

[Fernando Guallini]

Hi all,

Please, review the following change:

webrev: http://cr.openjdk.java.net/~joehw/jdk15/8183266/webrev/
bug: https://bugs.openjdk.java.net/browse/JDK-8183266

Change details:
- Added test coverage for XPathEvaluationResult.XPathResultType.getQNameType method
- Added type check for the getQNameType flow restricting the Number class subtypes to satisfy the spec (Integer, Double and Long)
- Updated equalsClassType method to be null safe.

Kind regards,
Fernando