* object.c (Init_Object): use rb_mod_init_copy for Class#initialize_copy

	* class.c (rb_class_init_copy): rename to class_init_copy_check, performs type
	  checks on arguments to prevent reinitialization of initialized class
	  [ruby-core:50869] [Bug #7557]

	* class.c (rb_mod_init_copy): use class_init_copy_check if receiver is T_CLASS

	* test/ruby/test_class.rb (class TestClass): related test


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@38507 b2dd03c8-39d4-4d8f-98ff-823fe69b080e