* iseq.c (iseq_data_to_ary): dump kw_arg as symbol

	* test/-ext-/iseq_load/test_iseq_load.rb: test kw_arg roundtrip
	  [ruby-core:69891] [Bug #11338]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@52783 b2dd03c8-39d4-4d8f-98ff-823fe69b080e