Fix gray stream issue for SBCL

The pretty printer seems to call the non-standard
stream-line-length generic function.

* swank-sbcl.lisp (sb-gray:stream-line-length): Implement default.
* swank-repl.lisp: Put swank-repl into its own package.
Use swank-repl: instead of swank: where needed.

* slime-repl.el, test/slime-repl-tests.el:
* test/slime-parse-tests.el (form-up-to-point.1): Don't
hardcode swank::%cursor-marker% use the slime-cursor-marker
constant instead.
Only test contribs that actually have tests.

* Makefile (CONTRIB_TESTS): New variable.
Merge branch 'master' into per-backend-packages

Conflicts:
	ChangeLog
	contrib/ChangeLog
Make presentations work, well compile, with swank-repl package.

* swank-repl.lisp: Export *send-repl-results-function*.
* swank-presentations.lisp (init-presentations): Move to function
so that *send-repl-results-function* is not clobbered as side
effect of compiling swank-presentation-streams.lisp
* swank-presentation-streams.lisp (init-presentation-streams):
Move to function so that *send-repl-results-function* is not
clobbered as side effect of compiling.
* slime-presentations.el (slime-presentations-on-connected): New.
* slime-presentation-streams.el
(slime-presentation-streams-on-connected): New.