Use a separate package for swank-gray.lisp.

Use gray streams also for CMUCL, SCL, and ABCL.

* lib/backend/swank-backend.lisp (gray-package-name): New interface function.
(import-from): Deleted. No longer used.
(*gray-stream-symbols*): Moved to swank-gray.lisp.
* lib/backend/swank-abcl.lisp, swank-cmucl.lisp, swank-scl.lisp
(gray-package-name): Implemented and delete old implementations of
make-input-stream and make-output-stream.
* lib/backend/swank-allegro.lisp, swank-ccl.lisp, swank-clisp, swank-ecl.lisp,
swan-lispworks.lisp, swank-sbcl.lisp,  (gray-package-name):
Implemented.
* lib/swank-gray.lisp: Make and use swank-gray package for this file.
* swank-loader.lisp (*sysdep-files*): Load swank-gray for CMUCL,
SCL, and ABCL.
* swank.asd (:swank): Load swank-gray for CMUCL, SCL, and ABCL.

(cherry picked from SLIME commit
17d3b585989c1e22dc6c25374f4e7e51336fdda1)

Conflicts:
	ChangeLog
	lib/lisp/backend/swank-abcl.lisp
	lib/lisp/backend/swank-cmucl.lisp
	lib/lisp/backend/swank-sbcl.lisp
	lib/lisp/backend/swank-scl.lisp
	swank-loader.lisp
Remove non-used optional gray stream methods.

* lib/lisp/swank-gray.lisp (stream-read-char-will-hang-p)
(stream-line-length): Deleted.

(cherry picked from SLIME commit
9528fb504a63b4d89ec0f3fb49771930f65a7b09)

Conflicts:
	ChangeLog
	lib/lisp/swank-gray.lisp
Make the ugly deadlock workaround even more ugly.

* lib/lisp/backend/swank-sbcl.lisp (stream-force-output): Create
swank-gray package early enough.

(cherry picked from SLIME commit
d65c16b8734690a56ea81d29fcd1f1c12c65bba1)

Conflicts:
	ChangeLog
	lib/lisp/backend/swank-sbcl.lisp
* swank-backend.lisp (gray-package-name): Fix docstring.

(cherry picked from SLIME commit
5b6ada970414906aa3158d8ba0aa1294f567d5ce)

Conflicts:
	ChangeLog
Globally rename the elisp destructure-case -> sly-dcase