Mention completion-wrap-movement in relevant commands

* lisp/simple.el (previous-completion, next-completion): Mention
`completion-wrap-movement'.

doc/emacs/mini.texi

@@ -381,6 +381,8 @@ used with the completion list:
 @vindex minibuffer-completion-auto-choose
 @item M-<down>
 @itemx @key{M-<up>}
+@findex previous-completion
+@findex next-completion
 These keys will navigate through the completions displayed in the
 completions buffer.  When @code{minibuffer-completion-auto-choose} is
 non-@code{nil} (which is the default), using these commands will

etc/NEWS

@@ -653,6 +653,7 @@ To enable this behavior, customize the user option
 'second-tab', then the first 'TAB' will display "*Completions*", and
 the second one will switch to the "*Completions*" buffer.
 
+---
 *** New user option 'completion-wrap-movement'.
 When non-nil, the commands 'next-completion' and 'previous-completion'
 automatically wrap around on reaching the beginning or the end of

lisp/simple.el

@@ -9208,14 +9208,18 @@ the completions is popped up and down."
 (defun previous-completion (n)
   "Move to the previous item in the completion list.
 With prefix argument N, move back N items (negative N means move
-forward)."
+forward).
+
+Also see the `completion-wrap-movement' variable."
   (interactive "p")
   (next-completion (- n)))
 
 (defun next-completion (n)
   "Move to the next item in the completion list.
 With prefix argument N, move N items (negative N means move
-backward)."
+backward).
+
+Also see the `completion-wrap-movement' variable."
   (interactive "p")
   (let ((prev (previous-single-property-change (point) 'mouse-face)))
     (goto-char (cond