merge revision(s) 39739: [Backport #8081]

	* object.c (Init_Object): remove Module#used, which has been
	  introduced in Ruby 2.0 by mistake.  [Bug #7916] [ruby-core:52719]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39951 b2dd03c8-39d4-4d8f-98ff-823fe69b080e