some things to do (not complete at all)

Martin:
** FUNCGEN **
- parameter for filenames
** AFD **
- common C++ source section (only solver access?)
- bidirectional explicite references 
- explicite references on default levels
- specification for expressions and references
- allow to hide abstract node types 
- solver generation
- access to (cmdline) parameters

Martin:
- Prop_Tree_Node::get_possible_children()
- optimization of Prop_Tree_Node::get_properties_names()
- Test functions for anything
- destruction of operator trees (with constant operands)

Wolfgang:
- Better POVRay support (yes, done when I can work with anitmt 
  so that I can effectively test things). 
- Clean up frame output code (better done when we implement the 
  new output concept). 
- fixme in fdump.cpp
- Parameter subsystem [...]
- Message handler: automatic newline, etc.
- message system support for all my parts
- message system & position objects ( & formatting / line break)
  (-fmessage-length...)
- More to come...
