Infer for fewer variables.

Improve error messages.
Extend csets to lists of maps.
Handle case-lambda arguments to poly funcs better.
Don't fail when there isn't a minimal substitution.

svn: r9573

original commit: 1449dec3727e591409f476ca4ddc9f8e96b3a102

collects/typed-scheme/private/base-env.ss

@@ -96,7 +96,7 @@
      (integer? (make-pred-ty -Integer))
      (boolean? (make-pred-ty B))
      (add1 (cl->*
-            #;(-> -Integer -Integer)
+            (-> -Integer -Integer)
             (-> N N)))
      (sub1 (cl->*
             #;(-> -Integer -Integer)