Update squid30 package to 3.0.18 (3.0.STABLE18).

It contains some critical problem of 3.0.17 and really fix security
problem according to updated SQUID-2009_2.txt.

Changes to squid-3.0.STABLE18 (04 Aug 2009):

- Bug 2728: regression: assertion failed: !eof
- Bug 2732: reply_body_max_size smaller than error page loops
            infinitely until out of memory
- Bug 2725: pconn failure if domain or client_address are unset
- Bug 2648: reserved helpers not shut down after reconfigure/rotate
- Bug 2462: make check should tell when cppunit is missing
- Remove excess messages about headers < minimum size
- Support Libtool 2.2.6

(taca)