Ulrich Neumerkel: add a docs/dir directory for people who want to use info there.

docs/dir

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+-*- Text -*-
+This is the file .../info/dir, which contains the topmost node of the
+Info hierarchy.  The first time you invoke Info you start off
+looking at that node, which is (dir)Top.
+
+File: dir      Node: Top       This is the top of the INFO tree
+  This (the Directory node) gives a menu of major topics.
+  Typing "d" returns here, "q" exits, "?" lists all INFO commands, "h"
+  gives a primer for first-timers, "mEmacs<Return>" visits the Emacs topic,
+  etc.
+  In Emacs, you can click mouse button 2 on a menu item or cross reference
+  to select it.
+  --- PLEASE ADD DOCUMENTATION TO THIS TREE. (See INFO topic first.) ---
+
+* Menu: The list of major topics begins on the next line.
+
+YAP Prolog
+* YAP Prolog Manual: (yap).                    YAP User's Manual.