it is possible to use Irssi::UI::Window::get_history_entries to save the
history entries, load_history_entries to load entries into the command
history and delete_history_entries to remove history entries (for example
to remove history selectively)
this allows access to the global history even when a using /window history
named or /set window_history on, and you want to recall something from one
of the other windows' histories.
usage (default): ctrl+up/down
