Allow explicit self-calls within classes

Allow writing self.f() within a class that has a method f. In a future
commit, this syntax will be required. For now, you can write either
self.f() or f().

I added a "privacy" field to all methods (whether class methods or not),
which allowed me to refactor the AST somewhat (getting rid of the
class_item type; now there's just class_member).

src/rustc/metadata/decoder.rs

@@ -431,7 +431,7 @@ fn get_iface_methods(cdata: cmd, id: ast::node_id, tcx: ty::ctxt)
                       'u' { ast::unsafe_fn }
                       'f' { ast::impure_fn }
                       'p' { ast::pure_fn }
-                    }}];
+                    }, privacy: ast::pub}];
     }
     @result
 }