Fix previous-button to work with connected buttons

[Diane Murray <disumu@x3y2z1.net>]

`previous-button' doesn't work correctly when two buttons inserted
with `insert-button' are right next to each other.  Instead of
returning the previous button, it skips it and returns the one before
it, even though there's no skip property set.  The following patch
fixes this.

Neither `previous-button' nor `next-button' work well with neighboring
buttons inserted with `insert-text-button' - this patch is *not* able
to solve that problem.


2007-03-11  Diane Murray  <disumu@x3y2z1.net>

	* button.el (previous-button): Fixed to work correctly when two
	overlay buttons are next to each other.


*** button.el	24 Jan 2007 13:01:15 +0100	1.22
--- button.el	11 Mar 2007 00:20:28 +0100	
***************
*** 371,377 ****
    (unless count-current
      (setq pos (previous-single-char-property-change pos 'button)))
    (and (> pos (point-min))
!        (or (button-at (1- pos))
  	   ;; We must have originally been on a button, and are now in
  	   ;; the inter-button space.  Recurse to find a button.
  	   (previous-button pos))))
--- 371,377 ----
    (unless count-current
      (setq pos (previous-single-char-property-change pos 'button)))
    (and (> pos (point-min))
!        (or (button-at pos)
  	   ;; We must have originally been on a button, and are now in
  	   ;; the inter-button space.  Recurse to find a button.
  	   (previous-button pos))))