[Bug-apl] New Input Mode

[Juergen Sauermann]

Hi,

as a preparation for the removal of libreadline I have created a new input mode for GNU APL.
The first shot (which is still a bit bumpy) is contained in SVN 454.

The new mode is enabled with --noRL. It will become the default (and --noRL will disappear when
the new mode is stable and readline has been removed.

The issues reported today have not been addressed yet, but will be taken care of.

The new mode is supposed to have similar (actually better) properties as readline:

- tab completion is more APL aware (⎕xx, user-defined symbols, )commands and more are considered)
- history (i.e. cursor up/down) is improved (eg. inside ∇ you can recall other function lines for editing).

Cursor key ESC sequences are currently hardwired - I will check if curses can be used instead.

/// Jürgen