merge revision(s) 42867: [Backport #8873]

	* variable.c (classname): the name of class that has
	  non class id should not be nil. This bug was introduced
	  in r36577.

	* test/thread/test_cv.rb: test for change.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@42911 b2dd03c8-39d4-4d8f-98ff-823fe69b080e