8227652: SetupOperatorNewDeleteCheck should discuss deleting destructors

[Kim Barrett]

Please review this explanatory comment being added to the description
of the check for using global operator new/delete in Hotspot code.
The described situation is somewhat obscure, and encountering it for
the first time (or again after a long time, as happened to me recently)
can be quite puzzling.

CR:
https://bugs.openjdk.java.net/browse/JDK-8227652

Webrev:
http://cr.openjdk.java.net/~kbarrett/8227652/open.00/