merge revision(s) 44583: [Backport #9302]

	* ext/thread/thread.c (rb_szqueue_push): check GET_SZQUEUE_WAITERS
	  instead of GET_QUEUE_WAITERS to prevent deadlock. Patch by Eric Wong.
	  [Bug #9302] [ruby-core:59324]

	* test/thread/test_queue.rb: add test


git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/branches/ruby_2_1@44847 b2dd03c8-39d4-4d8f-98ff-823fe69b080e