mmanon: added "]" to set of acceptable chars after an IPv4 address

This is used in Exim and Postfix ... and probably a bunch of other tools
closes: http://bugzilla.adiscon.com/show_bug.cgi?id=477
Thanks to Muri Cicanor for requesting the addition
mmanon: removed the check for specific "terminator characters" after last octet

As it turned out, this didn't work in practice as there
was an enormous set of potential terminator chars -- so removing
them was the best thing to do. Note that this may change behaviour of
existing installations. Yet, we still consider this an important
bugfix, that should be applied to the stable branch.