Fix a configure error when the IPFILTER option is selected. An example
of the error is:

checking for struct natlookup.nl_inipaddr.in6... no
checking for struct natlookup.nl_realipaddr.in6... eval: ${+...}: Bad substitution

> Script "configure" failed unexpectedly.

Please report the problem to timp87@gmail.com [maintainer] and attach the
"/export/wrkdir/amd64/export/home/cy/freebsd/git/ports/www/squid-devel/work/squid-4.0.25/config.log"
including the output of the failure of your make command. Also, it might be
a good idea to provide an overview of all packages installed on your system
(e.g. a /usr/local/sbin/pkg-static info -g -Ea).

• Error code 1

Stop.
make[1]: stopped in /export/home/cy/freebsd/git/ports/www/squid-devel

• Error code 1

Stop.
make: stopped in /export/home/cy/freebsd/git/ports/www/squid-devel

PR: 229244
Submitted by: cy
Reported by: cy
Approved by: Maintainer <timp87@gmail.com>