New Features as of Version 0.73

  Updated OpenContainers to version 1.4.3.  This adds some new
  features (see CHANGES in the OpenContainers directory).
  Most important:
     -added support for separated .h and .cc files for Val
     -added total ordering for Vals to fix SortedIterator bug.
     -added operator() for Val,HashTableT,AVLTreeT,andAVLHashT
      to throw an out_of_range exception when a key is not
      in the table (rather than inserting a default value).
     -added <,<=,>,>= for Array
     -added None, True, False to ValReader constants