Remove non-used optional gray stream methods.

* swank-gray.lisp (stream-read-char-will-hang-p)
(stream-line-length): Deleted.
Make the ugly deadlock workaround even more ugly.

* swank-sbcl.lisp (stream-force-output): Create swank-gray package
early enough.
* swank-backend.lisp (gray-package-name): Fix docstring.