RFR 8224716 : Javadoc of Int/Long/DoubleSummaryStatistics should mention possible overflow of count

[Ivan Gerasimov]

Hello!

In the implNote section of the javadoc for xxxSummaryStatistics classes 
it is mentioned that the sum is not checked for overflow.
It would be more accurate to add that neither does the implementation 
check the count for overflow.

Would you please help review this doc-only change?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8224716
WEBREV: http://cr.openjdk.java.net/~igerasim/8224716/00/webrev/

-- 
With kind regards,
Ivan Gerasimov