#20 Inputline should be modal

[Peter Hosey]

a'la the InputSaver plug-in: the inputline should maintain separate buffers for each window, even if only one global inputline is in effect. (this might be implemented at the user level as a third option, e.g.:

( ) One inputline in each window
( ) One inputline for all windows
(+) One inputline for all windows, but separate buffers for each