iprange: do accept non-ranges for xt_iprange v1 (log)

Details for commit v1.4.5-11-ga10a12a:

"When upgraded to new lenny kernel from 2.6.24 from etch'n'half
iprange now does not allow to use single ip-address as its argument:

	# iptables -A FORWARD -m iprange --src-range 192.168.0.0"

References: http://bugs.debian.org/547139

What we have here is that the user is now using iprange v1 from
previously v0.
Add recognition for single addresses to v1.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>