Fix bug #17560 with backward-incompatible API change in rmail-delete-*.

 lisp/mail/rmail.el (rmail-delete-forward, rmail-delete-backward): The
 argument COUNT is now optional, to be more backward-compatible.
 Doc fix.

 etc/NEWS: Document the API change.

etc/NEWS

@@ -146,6 +146,9 @@ permissions set to temporary values (e.g., for creating private files).
 
 ** You can access the slots of structures using `cl-struct-slot-value'.
 
+** Functions `rmail-delete-forward' and `rmail-delete-backward' take an
+optional repeat-count argument.
+
 
 * Changes in Emacs 24.5 on Non-Free Operating Systems
 

lisp/ChangeLog

+2014-05-30    Ken Olum  <kdo@cosmos.phy.tufts.edu>  (tiny change)
+
+	* mail/rmail.el (rmail-delete-forward, rmail-delete-backward): The
+	argument COUNT is now optional, to be more backward-compatible.
+	Doc fix.  (Bug#17560)
+
 2014-05-29  Reuben Thomas  <rrt@sc3d.org>
 	* whitespace.el (whitespace-report-region): Simplify

lisp/mail/rmail.el

@@ -3476,11 +3476,12 @@ STATE non-nil means mark as deleted."
 (defun rmail-delete-forward (&optional count)
   "Delete this message and move to next nondeleted one.
 Deleted messages stay in the file until the \\[rmail-expunge] command is given.
-A prefix argument is a repeat count;
+Optional argument COUNT (interactively, prefix argument) is a repeat count;
 negative argument means move backwards instead of forwards.
 
 Returns t if a new message is displayed after the delete, or nil otherwise."
   (interactive "p")
+  (if (not count) (setq count 1))
   (let (value backward)
     (if (< count 0)
 	(setq count (- count) backward t))
@@ -3495,15 +3496,16 @@ Returns t if a new message is displayed after the delete, or nil otherwise."
     (rmail-maybe-display-summary)
     value))
 
-(defun rmail-delete-backward (count)
+(defun rmail-delete-backward (&optional count)
   "Delete this message and move to previous nondeleted one.
 Deleted messages stay in the file until the \\[rmail-expunge] command is given.
-A prefix argument is a repeat count;
+Optional argument COUNT (interactively, prefix argument) is a repeat count;
 negative argument means move forwards instead of backwards.
 
 Returns t if a new message is displayed after the delete, or nil otherwise."
 
   (interactive "p")
+  (if (not count) (setq count 1))
   (rmail-delete-forward (- count)))
 
 ;; Expunging.