Maps known navigation keywords (:up :down :left :right :enter :backspace :tab
:escape :home :end :ppage :npage) explicitly in the case to bypass the guard,
so only non-keyword, non-navigation values are filtered. This prevents :CTRL-A
(byte 1/SOH) from ever reaching on-key or dispatch-key-event and resetting
cursor-pos to 0 via the :ctrl+a keymap binding.
Amr Gharbeia
8c29c228cd