libipq : Not used any more. ( Since year 2006 ? )
http://en.wikipedia.org/wiki/Libipq :
"Libipq has been deprecated in favour of the newer libnetfilter_queue
in Linux kernel-2.6.14 onwards."
/configure --help: --enable-libipq : Just an old text, I guess.
( Or : may be used for a kernel before 2.6.14 ).
.