core: Rename to_mut and from_mut to cast_to_mut and cast_from_mut

src/libsyntax/attr.rs

@@ -304,9 +304,9 @@ fn sort_meta_items(+items: ~[@ast::meta_item]) -> ~[@ast::meta_item] {
     }
 
     // This is sort of stupid here, converting to a vec of mutables and back
-    let v: ~[mut @ast::meta_item] = vec::to_mut(items);
+    let v: ~[mut @ast::meta_item] = vec::cast_to_mut(items);
     std::sort::quick_sort(v, lteq);
-    vec::from_mut(move v)
+    vec::cast_from_mut(move v)
 }
 
 fn remove_meta_items_by_name(items: ~[@ast::meta_item], name: ~str) ->