merge revision(s) 44501: [Backport #9353]

	* struct.c (rb_struct_set): return assigned value from setter method
	  rather than struct object. [Bug #9353] [ruby-core:59509]

	* test/ruby/test_struct.rb (test_setter_method_returns_value): add test


git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/branches/ruby_2_1@44826 b2dd03c8-39d4-4d8f-98ff-823fe69b080e