Remove specific byte-compiler warnings for cl.el

Remove specific byte-compiler warnings for cl.el

* lisp/emacs-lisp/bytecomp.el (byte-compile-warning-types)
(byte-compile-warnings, byte-compile-cl-file-p)
(byte-compile-eval, byte-compile-eval-before-compile)
(byte-compile-arglist-warn, byte-compile-find-cl-functions)
(byte-compile-cl-warn, displaying-byte-compile-warnings)
(byte-compile-file-form-require, byte-compile-form): Remove all
specific cl.el warnings, as that library is now obsolete.  The
regular obsoletion warnings are sufficiently discouraging.
* lisp/emacs-lisp/advice.el (ad-compile-function): Don't try to
silence the now removed warning.
* doc/lispref/tips.texi (Coding Conventions):
* doc/misc/cl.texi (Organization): Make recommendation to not use
cl.el and cl-compat.el stronger.
* lisp/obsolete/cl.el: Make alias help say that they are obsolete.
* lisp/obsolete/cl-compat.el (build-klist, safe-idiv)
(pair-with-newsyms): Silence byte-compiler.