Revert "Merge pull request #242 from
jsx/kazuho/experiments/redefine-nodejs-streams" since it might cause
compatibility problems bet. existing users (esp. the renaming of
"Stream" class)

This reverts commit b560b3f5cf6642eb8ba50ebeff792fbec04c3c23, reversing
changes made to 7136124d46d40fb27221438d0fc5513e6c742183.
no need to reorder definition of native classes (cherry-picked from the
reverted branch)