Explicitly require cl-lib where needed

Rather than relying on the byte-compiler happening to use it.
* lisp/completion.el, lisp/ffap.el, lisp/loadhist.el:
* lisp/userlock.el, lisp/emacs-lisp/debug.el, lisp/emacs-lisp/rx.el:
* lisp/emacs-lisp/testcover.el, lisp/mail/rfc2231.el:
* lisp/net/newst-treeview.el, lisp/net/puny.el:
* lisp/net/tramp-archive.el, lisp/net/tramp-gvfs.el:
* lisp/net/tramp-sh.el, lisp/net/tramp-smb.el, lisp/org/org-ctags.el:
* lisp/org/org-macs.el, lisp/progmodes/grep.el:
* lisp/progmodes/perl-mode.el, lisp/progmodes/ruby-mode.el:
* lisp/textmodes/dns-mode.el, lisp/textmodes/mhtml-mode.el:
* lisp/vc/pcvs-parse.el: Explicitly require cl-lib as needed.

lisp/emacs-lisp/debug.el

@@ -27,6 +27,7 @@
 
 ;;; Code:
 
+(require 'cl-lib)
 (require 'button)
 
 (defgroup debugger nil

lisp/emacs-lisp/rx.el

@@ -106,6 +106,8 @@
 
 ;;; Code:
 
+(require 'cl-lib)
+
 ;; FIXME: support macros.
 
 (defvar rx-constituents              ;Not `const' because some modes extend it.

lisp/emacs-lisp/testcover.el

@@ -63,6 +63,7 @@
 ;;   error if these "potentially" 1-valued forms actually return differing
 ;;   values.
 
+(eval-when-compile (require 'cl-lib))
 (require 'edebug)
 (provide 'testcover)