Fix more warnings when compiling files alone

* slime-tests.el (cl): require it when compiling.
(def-slime-test): use cl-loop and fix indentation.

* slime.el: Require 'cl but only when compiling.

* slime.el (outline, etags): require them at load time, too.
(slime-setup): Use new `slime-contribs' directly, not obsolete
alias.
(slime-required-modules): Move up to avoid warning.