call it when the server is in setup_protocol().  The function sets
  allow_inc_recurse to 0 if some options won't allow us to support
  an incremental-recursive transfer.
- The server now checks for an 'i' in the -e option from the client
  and zeros out allow_inc_recurse if not found.
- The server reports its inc_recurse determination back to the client.
- The client sets inc_recurse based on the value it gets from the server.