separate options, prefix and prefix2. This simplifies the code and gets
rid the data options type which was only used for this one option.
Also add a -2 flag to send-prefix to send the secondary prefix key,
fixing a cause of minor irritation.
People who want three prefix keys are out of luck :-).
terminal to be switched between several different windows and programs
displayed on one terminal be detached from one terminal and moved to another.
ok deraadt pirofti