Remove the glob/shadowing exception bug

[breaking-change]

This and the other commit in this PR change the rules for shadowing and globs to be
stricter. There were previously bugs where some glob imports would not be checked
for shadowing. Those are now fixed and you may have to adjust your imports to use
fewer globs.

Author: nrc

src/librustc_resolve/lib.rs

@@ -345,9 +345,6 @@ impl Rib {
 #[deriving(Show,PartialEq,Clone,Copy)]
 enum Shadowable {
     Always,
-    /// Means that the recorded import obeys the glob shadowing rules, i.e., can
-    /// only be shadowed by another glob import.
-    Glob,
     Never
 }
 
@@ -1719,11 +1716,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                                     view_path.span,
                                                     id,
                                                     is_public,
-                                                    if shadowable == Shadowable::Never {
-                                                        Shadowable::Glob
-                                                    } else {
-                                                        shadowable
-                                                    });
+                                                    shadowable);
                     }
                 }
             }