Remove some home-grown copies of cl-lib functions.

* lisp/org.el (org-count, org-remove-if, org-remove-if-not):
(org-reduce, org-every, org-some): Obsolete, use cl-lib versions
everywhere.
(org-sublist): Reimplement in terms of `cl-subseq'; make obsolete.

org-contacts.el

@@ -593,7 +593,7 @@ description."
 (defun org-contacts-remove-ignored-property-values (ignore-list list)
   "Remove all ignore-list's elements from list and you can use
    regular expressions in the ignore list."
-    (org-remove-if (lambda (el)
+    (cl-remove-if (lambda (el)
 		     (org-find-if (lambda (x)
 				    (string-match-p x el))
 				  ignore-list))