"Listen6" and "Listen4" now do what the name implies and "Listen" listens on
both ipv4 and ipv6 (unless a bind host was set which forces something
different).
This also changes webadmin appropriately.
Thanks to DarthGandalf for the idea and the patch.
git-svn-id: https://znc.svn.sourceforge.net/svnroot/znc/trunk@1816 726aef4b-f618-498e-8847-2d620e286838