RFR (M) 8024438: JSR 292 API specification maintenance for JDK 8

[John Rose]

http://cr.openjdk.java.net/~jrose/8024438/webrev.00

These are miscellaneous edits to javadoc and unit tests, clarifying various minor corner cases and improving presentation.

There is also a single API change (already under review by CCC): Adding a missing wildcard to Constructor<?>.

Please review.

Thanks,
— John