merge revision(s) 41175: [Backport #8503]

	* class.c (include_modules_at): invalidate method cache if included
	  module contains constants

	* test/ruby/test_module.rb: add test


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@41645 b2dd03c8-39d4-4d8f-98ff-823fe69b080e