(ielm-return): Support it.
(ielm-print-working-buffer): New command
(ielm-change-working-buffer): New command
(ielm-display-working-buffer): New command
(ielm-map): Bindings for new commands; bindings from
shared-lisp-mode-map; Lemacs support.
(ielm-eval-input): Give bindings in scope during the eval
non-clashing names (ielm- prefix)
(ielm-get-old-input): New function
(inferior-emacs-lisp-mode): Bind it to comint-get-old-input