Mark all channels as read in IRSSI

Sometimes it could be annoying to see your task bar full of updates mostly due to people entering or quitting the channel.

To be able to clean your task bar at once, you can configure this alias:

/alias READ script exec \$_->activity(0) for Irssi::windows

Source: http://pthree.org/2011/08/18/pimp-my-irssi-part-2/