skolem_fact/thm: uniform numbering, even for singleton list;
declare_skofuns: eliminated recovery via Clausify_failure -- should be sufficiently robust as is;
;;;
;;; $Id$
;;;
;;; Options for Proof General
;; Examples for sensible settings:
;(custom-set-variables '(isar-eta-contract nil))
;(custom-set-faces
; '(proof-locked-face
; ((((type x) (class color) (background light)) (:background "lightsteelblue2")))))