Use the libreadline in Winedbg, if available

[Ove Kaaven]

On Mon, 18 Jun 2001, Patrik Stridvall wrote:

> A minor notice. Readline is GPL:ed (not LGPL:ed) which is not so good.
> While it is without doubt legal for us to use and distribute,
> it might cause trouble for other people.

Not as long as it's optional (that patch even supported ./configure
--without-readline, so no trouble, such people would just disable it).