ADT Lib Update

[Michael van Acken <mvacken@t-online.de>]

I added the modules StackLL and QueueLL to the library.  Both modules
are derived from Tim's proposal with just minor editing.  The current
list of modules is still rather short:

MODULE libadt;

IMPORT
  AcObject,     (* abstract root of class hierarchie *)
  AcObjFct,     (* abstract functions on objects and standard functions *)
  AcContainer,  (* abstract base type for all container classes *)
  AcRider,      (* abstract rider for container classes *)
  
  Alien,        (* auxiliary class for module `Storage'; implemented & tested*)
  Storage,      (* framework for persistent objects; implemented & tested *)
  
  String,       (* dynamic strings; implemented, untested *)
  
  ListSL,       (* single linked list; specified, not implemented *)
  ListDL,       (* double linked list; implemented, untested *)
  StackLL,      (* stack using linked list; specified, not implemented *)
  QueueLL;      (* queue using linked list; specified, not implemented *)
  
END libadt.

As you can see, for every import there is a short comment describing
the module and its status.  Status can be one of the following:

  draft
    draft of a possible module specification

  specified, not implemented
    no longer draft status, meaning the interface has been determined;
    none or only parts of the procedures are implemented

  implemented, untested
    all procedures are implemented, but they have not been tested yet;
    adding untested code to the library is a privilege of the library
    coordinator :-)

  implemented & tested
    module has been tested and is believed to work correctly

I will accept contributions on all levels.  I would like to get
further module drafts, implementations of the specified modules, and
feedback on successful use of any of the modules.

The current sources are available at
http://home.t-online.de/home/mvacken

-- mva