Documentation for ForkJoinPool class

[Dmitry Zhikharev]

Hi!

ForkJoinPool class documentation says nothing about it using daemon threads since Java 8 (https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ForkJoinPool.html, see also http://hg.openjdk.java.net/jdk9/jdk9/jdk/file/0086eb10182b/src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java).
It was there in Java 7 documentation: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ForkJoinPool.html (see "Sample Usage").

I think it's an important note about ForkJoinPool and should be added back.

Regards, Dmitry Zhikharev