RFR (XS) 8228352 : CANON_EQ breaks when pattern contains supplementary codepoint

[Ivan Gerasimov]

Hello!

Pattern.compile fails with IOOB when normalizing a pattern that contains 
a surrogate pair.

Would you please help review a trivial 1-line fix?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8228352
WEBREV: http://cr.openjdk.java.net/~igerasim/8228352/00/webrev/

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With kind regards,
Ivan Gerasimov