bug#10771: TAB completion for info-display-manual

[Juri Linkov]

> Because manuals loaded into my Info buffers do not necessarily reflect
> Info files on my disk.

Is this because you delete Info files from the disk leaving open
their Info buffers?  I'm not sure whether additional complexity
is necessary to handle completion for such rare cases, but at least
the minibuffer should allow you to enter such manual names.
I mean changing the REQUIRE-MATCH arg of `completing-read' from t to nil,
so you can still enter these manual names like at the time when
this command accepted a plain string before the latest change.

=== modified file 'lisp/info.el'
--- lisp/info.el        2012-12-02 20:07:04 +0000
+++ lisp/info.el        2012-12-02 21:11:17 +0000
@@ -5138,7 +5138,7 @@ (defun info-display-manual (manual)
                       (apply-partially 'Info-read-node-name-2
                                        Info-directory-list
                                        (mapcar 'car Info-suffix-list))
-                      nil t))))
+                      nil nil))))
   (let ((blist (buffer-list))
        (manual-re (concat "\\(/\\|\\`\\)" manual "\\(\\.\\|\\'\\)"))
        (case-fold-search t)