RFR: 8063147: Class.getFields spec should state that fields are inherited from superinterfaces

[Martin Buchholz]

Hi Joe,

I'd like you to do a code review.

https://bugs.openjdk.java.net/browse/JDK-8063147
Webrev: 
http://cr.openjdk.java.net/~martin/webrevs/openjdk9/Class-getFields-spec/

getFields was embarrassingly undertested, so I added some.

Please shepherd through CCC.