object.c: undef Module#prepend_features on Class

* object.c (Init_Object): undef Module#prepend_features on Class, as
  well as Module#append_features.  [Fixes GH-376]
* test_class.rb: Added test for above. And ensure type checking
  on similar methods as module_function.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42541 b2dd03c8-39d4-4d8f-98ff-823fe69b080e