eta-expand built-in constants; also rewrite partially applied natural number terms
;;; Options for Proof General
;; Examples for sensible settings:
(custom-set-variables '(indent-tabs-mode nil))
;(custom-set-variables '(isar-eta-contract nil))
;(custom-set-faces
; '(proof-locked-face
; ((((type x) (class color) (background light)) (:background "lightsteelblue2")))))