Agenda: Make prefix argument to `org-agenda' optional.

This is to make it easier to call this function from lisp.

Patch by Eric Schulte.

lisp/ChangeLog

@@ -1,5 +1,7 @@
 2009-02-25  Carsten Dominik  <carsten.dominik@gmail.com>
 
+	* org-agenda.el (org-agenda): Make prefix arg optional.
+
 	* org-table.el (orgtbl-self-insert-command): Cluster undo for 20
 	characters.
 

lisp/org-agenda.el

@@ -1444,7 +1444,7 @@ that have been changed along."
 (defvar org-agenda-overriding-restriction nil)
 
 ;;;###autoload
-(defun org-agenda (arg &optional keys restriction)
+(defun org-agenda (&optional arg keys restriction)
   "Dispatch agenda commands to collect entries to the agenda buffer.
 Prompts for a command to execute.  Any prefix arg will be passed
 on to the selected command.  The default selections are: