RFR [8035975] Pattern.compile(String, int) fails to throw IllegalArgumentException

[Ivan Gerasimov]

Hello!

The javadoc says that Pattern.compile(String regex, int flag) will throw 
IllegalArgumentException, if flag contains an invalid bit set.
However, it fails to do so.

Would you please help review the simple fix for that?
Alternatively, we could just remove the corresponding @throws part, but 
that would change the spec.

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8035975
WEBREV: http://cr.openjdk.java.net/~igerasim/8035975/0/webrev/

Sincerely yours,
Ivan