libraries/prompter: Fix auto-return-p.
libraries/prompter: Fix auto-return-p.

Example:

(prompt :prompt "Test prompt"
				 :auto-return-p t
				 :sources (list (make-instance 'prompter:source :name "Test"
																												:constructor '("fooooo" "barrrrr"))))

Previously, pressing "fo" would not return.

jmercouris/NeXT,jmercouris/NeXT