Be more conservative with regular expressions.

Starting with a non-greedy universal match causes Java's regular expression
engine to try to match zero characters followed by the rest of the pattern,
then 1 character followed by the rest of the pattern, and so on until it finds
a match. Since comments must appear at the _end_ of input, this ensures that
the regex engine does a maximal amount of work before eliminating a comment.
For queries of a "reasonable" size, this isn't an issue, but a 10 or 20
kilocharacter query is large enough to cause comment removal to take over a
second.

Since the replacement removes the trailing part of the match outright, I've
rewritten the filter regexes to do so directly, rather than by replacing the
trailing part with the preceding universal group, and removed the universal
group match. This permits the regex engine to skip from whitespace to
whitespace without evaluating all the intervening bytes, and avoids
backtracking entirely.

This bit my day job, in real life, on queries that insert entire PNG images
via hex-encoded strings. While this is an unreasonable query, it's not an
_unrealistic_ query. We worked around the problem by disabling stripComments,
but fixing the regex will improve overall performance.
Merge pull request #109 from ojacobson/stripComments-regex-performance

Be more conservative with regular expressions in stripComments.