(recentf-open-files-item): Include newline in button

field, so opening a file will work, when the point is at the end
of the file name.  Allow, for example, to [i]search a file by
extension and just push RET to open it.

lisp/recentf.el

@@ -1165,7 +1165,7 @@ IGNORE other arguments."
            :button-prefix ""
            :button-suffix ""
            :button-face default
-           :format "%[%t%]\n"
+           :format "%[%t\n%]"
            :help-echo ,(concat "Open " (cdr menu-element))
            :action recentf-open-files-action
            ,(cdr menu-element))))