This file is the rough beginning of a set of PIL tree classes.

xFoo leading-"x" field names are used in nameless (array-based) nodes where I don't yet know an authoritative name.

30 Aug 2005 - some notes on macros:

   Ideally, the node definition clauses would be in one file,
   and the defining macros, for each of various class hierarchies,
   in others.  But we cant do that yet.

   And since macros cannot currently define classes,
      macro f($x) { "class $x \{};" }  f("C");  C.new
      Error: No compatible subroutine found: "&C" 
   this file is currently simply a source code generator.
   Which also addresses the problem that macros are currently
   quite slow (~10sec for this file).

   And because macros are buggy, the node_Mumble macros are
   currently defined as subs, which we can get away with since
   this is currently simply a code generator.