Fix existing privacy/visibility violations

This commit fixes all of the fallout of the previous commit which is an attempt
to refine privacy. There were a few unfortunate leaks which now must be plugged,
and the most horrible one is the current `shouldnt_be_public` module now inside
`std::rt`. I think that this either needs a slight reorganization of the
runtime, or otherwise it needs to just wait for the external users of these
modules to get replaced with their `rt` implementations.

Other fixes involve making things pub which should be pub, and otherwise
updating error messages that now reference privacy instead of referencing an
"unresolved name" (yay!).

src/libsyntax/ast_util.rs

@@ -964,7 +964,7 @@ mod test {
     use super::*;
     use std::io;
     use opt_vec;
-    use std::hash::HashMap;
+    use std::hashmap::HashMap;
 
     fn ident_to_segment(id : &Ident) -> PathSegment {
         PathSegment{identifier:id.clone(), lifetime: None, types: opt_vec::Empty}