Fix recently introduced crash on MS-Windows (Bug#12839).

* w32term.h (struct scroll_bar): Use convenient header.
(SCROLL_BAR_VEC_SIZE): Remove.
* w32term.c (x_scroll_bar_create): Use VECSIZE.

src/ChangeLog

+2012-11-09  Dmitry Antipov  <dmantipov@yandex.ru>
+
+	Fix recently introduced crash on MS-Windows (Bug#12839).
+	* w32term.h (struct scroll_bar): Use convenient header.
+	(SCROLL_BAR_VEC_SIZE): Remove.
+	* w32term.c (x_scroll_bar_create): Use VECSIZE.
+
 2012-11-09  Dmitry Antipov  <dmantipov@yandex.ru>
 	Tweak last vectorlike_header change.

src/w32term.c

@@ -3626,7 +3626,7 @@ x_scroll_bar_create (struct window *w, int top, int left, int width, int height)
   HWND hwnd;
   SCROLLINFO si;
   struct scroll_bar *bar
-    = XSCROLL_BAR (Fmake_vector (make_number (SCROLL_BAR_VEC_SIZE), Qnil));
+    = XSCROLL_BAR (Fmake_vector (make_number (VECSIZE (struct scroll_bar)), Qnil));
   Lisp_Object barobj;
 
   block_input ();

src/w32term.h

@@ -415,9 +415,8 @@ extern struct w32_output w32term_display;
 
 struct scroll_bar {
 
-  /* These fields are shared by all vectors.  */
-  EMACS_INT size_from_Lisp_Vector_struct;
-  struct Lisp_Vector *next_from_Lisp_Vector_struct;
+  /* This field is shared by all vectors.  */
+  struct vectorlike_header header;
 
   /* The window we're a scroll bar for.  */
   Lisp_Object window;
@@ -460,12 +459,6 @@ struct scroll_bar {
   Lisp_Object fringe_extended_p;
 };
 
-/* The number of elements a vector holding a struct scroll_bar needs.  */
-#define SCROLL_BAR_VEC_SIZE					\
-  ((sizeof (struct scroll_bar)					\
-    - sizeof (EMACS_INT) - sizeof (struct Lisp_Vector *))	\
-   / word_size)
-
 /* Turning a lisp vector value into a pointer to a struct scroll_bar.  */
 #define XSCROLL_BAR(vec) ((struct scroll_bar *) XVECTOR (vec))