merge revision(s) r47191: [Backport #10140]

	* iseq.c (rb_iseq_clone): Should not insert write barrier from
	  non-RVALUE data (to non-RVALUE data, of course).
	  Ruby 2.1 also has a same problem.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@47481 b2dd03c8-39d4-4d8f-98ff-823fe69b080e