SCAT language components
------------------------

   * rpn syntax transformer
   * state representation (stack + hidden)
   * prefix namespace management
   * scheme function snarfing
   * defining scat compositions


Highlevel interface
-------------------

   (scat: . <src>)

     Create an anonymous SCAT function.

   (compositions <ns> <compiler> . ((<name> . <src>) ...))

     Create a collection of function objects from source code <src>,
     and bind them to <name> in the namespace <ns>, using the compiler
     (<compiler> . <src>). The compiler handles the source namespace.

   (snarf <snarfer> <ns> . <spec>)

     Snarf functionality from scheme into namespace <ns> using the
     <snarfer> transformer.


