Adding nested guard test from Per Bothner.
Adding a default mode for create-directory.
Accepting begin in addition to body library decl in analyze-module.
Hygiene change. Removing syntactic closure flattening to
support unhygienic insertion.  Breaks the previous assumption
that syntactic closures were never nested.
Using lowercase digits by default in (show (written ...)).
Removing unused env-monad bindings.