merge revision(s) r45302: [Backport #9616]

	* class.c (rb_class_subclass_add): use xmalloc

	* class.c (rb_module_add_to_subclasses_list): ditto

	* class.c (rb_class_remove_from_super_subclasses): use xfree

	* class.c (rb_class_remove_from_module_subclasses): ditto
	  [Bug #9616]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@46319 b2dd03c8-39d4-4d8f-98ff-823fe69b080e