RFR 8230829 : Matcher matches a surrogate pair that crosses border of the region

[Ivan Gerasimov]

Hello!

When the regex.Matcher matches a supplementary codepoint, it may 
inadvertently cross the border of the explicitly specified region 
without noticing.

Would you please help review a simple fix?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8230829
WEBREV: http://cr.openjdk.java.net/~igerasim/8230829/00/webrev/

Thanks in advance!

-- 
With kind regards,
Ivan Gerasimov