ObjectSpace.total_memsize_of_all_objects() to
  ObjectSpace.memsize_of_all([klass]).
  Accept Class object to filter the objects.
* test/objspace/test_objspace.rb: fix test for above change.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29624 b2dd03c8-39d4-4d8f-98ff-823fe69b080e