Tue Nov 8 13:12:58 EST 2011

General cleanup

- Error messages are horrible.  Some examples:

   duplicate definition
   -> where's the first one?)

   non-null-compilation-stack:  (#<target-word>)
   -> say where the context is opened, i.e. the location of the non-matched "for"

- .f files are not in dependencies for compilation of .fm module.

- ! and @ only work for macros.  how to fix that?