Main future issue:
 - allow free EVars so queries can be checked after reconstruction
 - will not always raise Error gracefully on ill-typed terms
 - does not check consistent EVar assignment

CM/
README
WALK
sources.cm    OK -fp
	      OK -cs
strict.fun    OK -fp
	      OK -cs
strict.sig    OK -fp
      	      OK -cs
typecheck.fun OK -fp
	      Q: only closed term type checkable? LATER
	      OK -cs
typecheck.sig OK -fp
	      OK -cs
typecheck.sml OK -fp
	      OK -cs