Make kttcp work in -stable (and -current)

Make kttcp work in -stable (and -current)

- Removed kttcp_sosend() and kttcp_soreceive() in favor of using
  sosend() / soreceive() with UIO_NOCOPY.  The locking changes in the
  socket layer make merging the kttcp_so* and the so* routines a real
  pain.  It was a lot easier to just use the integrated routines.

- Eliminated KTTCP_MAX_XMIT restrictions on send and receive sizes
  because I encountered no problems with streams larger than MAX_INT.
  MAX_INT bytes is only good for a few seconds at 4Gb/sec ;)

- Removed Giant from send / recv routines.

- Fixed character device protos, cdevsw init, etc, to work in 5.x /
  6.x

Reviewed by: sam
MFC after: 1 week