* contrib/sly-clipboard.el: Require `cl-lib'/`cl' for `lexical-let' and `cl-'
prefix.
(sly-clipboard-insert-entries, sly-clipboard-insert-ref)
(sly-clipboard-ref-modified): Use `cl-' prefix.

(cherry picked from SLIME commit
080caca5)

Conflicts:
	contrib/ChangeLog
	contrib/slime-clipboard.el