(indent-region): Make COLUMN arg optional.

lisp/indent.el

@@ -322,9 +322,9 @@ line, but does not move past any whitespace that was explicitly inserted
   "Short cut function to indent region using `indent-according-to-mode'.
 A value of nil means really run `indent-according-to-mode' on each line.")
 
-(defun indent-region (start end column)
+(defun indent-region (start end &optional column)
   "Indent each nonblank line in the region.
-With prefix no argument, indent each line using `indent-according-to-mode',
+With no prefix argument, indent each line using `indent-according-to-mode',
 or use `indent-region-function' to do the whole region if that's non-nil.
 If there is a fill prefix, make each line start with the fill prefix.
 With argument COLUMN, indent each line to that column.