Merge pull request #759 from kachick/alias_method_checks_frozen

Module#alias_method should raise a RuntimeError on frozen instance

spec/tags/core/module/alias_method_tags.txt

@@ -1,4 +1,3 @@
 fails:Module#alias_method retains method visibility
 fails:Module#alias_method fails if origin method not found
-fails:Module#alias_method raises RuntimeError if frozen
 fails:Module#alias_method is a private method

topaz/objects/moduleobject.py

@@ -487,6 +487,7 @@ def method_public_class_method(self, space, w_name):
         return space.send(w_cls, "public", [w_name])
 
     @classdef.method("alias_method", new_name="symbol", old_name="symbol")
+    @check_frozen()
     def method_alias_method(self, space, new_name, old_name):
         w_method = self.find_method(space, old_name)
         if w_method is None: