merge revision(s) r45308,r45316: [Backport #9621]

	* ext/objspace/objspace_dump.c: Check fptr before trying to dump RFILE
	  object fd. [GH-562]

	* test/objspace/test_objspace.rb: add test

	* test/objspace/test_objspace.rb (TestObjSpace#test_dump_uninitialized_file):
	  remove dependency on json library.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@46403 b2dd03c8-39d4-4d8f-98ff-823fe69b080e