in default.theme.
If some abstract isn't set in theme, it fallbacks to the one in
default.theme now. This should help with old themes, and maybe themes
that don't change something should just keep those parts commented out..
git-svn-id: http://svn.irssi.org/repos/irssi/trunk@1386 dbcabf3a-b0e7-0310-adc4-f8d773084564