Use cl-lib in slime-fuzzy.el and fix bugs in slime-package-fu.el

```
	* slime-package-fu.el (slime-defpackage-exports): Handle strings
	in (:export ...) clause.
	(slime-frob-defpackage-form): Do not skip the package name.

	* slime-fuzzy.el (slime-fuzzy-completions)
	(slime-fuzzy-complete-symbol)
	(slime-fuzzy-insert-completion-choice)
	(slime-fuzzy-fill-completions-buffer)
	(slime-fuzzy-insert-from-point, slime-fuzzy-select): Use cl-lib.
```