rework RevThreadSpawn without TeeInput and 1.8 support
Exposing a synchronous interface is too complicated for too
little gain. Given the following factors:
* basic ThreadSpawn performs admirably under REE 1.8
* both ThreadSpawn and Revactor work well under 1.9
* few applications/requests actually need a streaming "rack.input"
We've decided its not worth the effort to attempt to support
streaming rack.input at the moment. Instead, the new
RevThreadSpawn model performs much better for most applications
under Ruby 1.9