signals broke something :) -window option to /JOIN and /QUERY. This
time don't check for any item with same server/name, but check that the
item itself doesn't have window set yet.
git-svn-id: http://svn.irssi.org/repos/irssi/trunk@1326 dbcabf3a-b0e7-0310-adc4-f8d773084564