Support for exclamation mark missing in regexp

with HIVE-6013 gets support for regular expressions. However, die ! character is valid, too. It is needed for expressions like

set hive.support.quoted.identifiers = none;
select `^(?!donotuseme).*$` from table;

which is the idiom to select all but column donotuseme .

See http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html for a reference of supported chars in Java regexp.

The patch simply fixes the lexer to support '!' as REGEX char. And does simply work.

Please review.

If you like to have an iTest for it, I beg you to help me. I tried several days on a different issue to figure out how it is supposed to work and failed miserably.