bluray: use a reference of internal pictures instead of picture copy

The picture inside our internal regions is refcounted, so it will stay alive
even if the internal region is deleted.

This will make things a bit faster and use less memory.

modules/access/bluray.c

@@ -1674,17 +1674,26 @@ static void subpictureUpdaterUpdate(subpicture_t *p_subpic,
      * When this function is called, all p_subpic regions are gone.
      * We need to duplicate our regions (stored internally) to this subpic.
      */
-    subpicture_region_t *p_src;
+    const subpicture_region_t *p_src;
     if (vlc_spu_regions_is_empty(&p_overlay->regions)) {
         updater_unlock_overlay(p_upd_sys);
         return;
     }
 
     subpicture_region_t *p_dst;
-    vlc_spu_regions_foreach(p_src, &p_overlay->regions) {
-        p_dst = subpicture_region_Copy(p_src);
+    vlc_spu_regions_foreach_const(p_src, &p_overlay->regions) {
+        p_dst = subpicture_region_ForPicture(&p_src->fmt, p_src->p_picture);
         if (p_dst == NULL)
             break;
+
+        p_dst->i_x      = p_src->i_x;
+        p_dst->i_y      = p_src->i_y;
+        // fields not modified on the source
+        p_dst->i_align  = p_src->i_align;
+        p_dst->i_alpha  = p_src->i_alpha;
+        p_dst->zoom_h   = p_src->zoom_h;
+        p_dst->zoom_v   = p_src->zoom_v;
+
         vlc_spu_regions_push(&p_subpic->regions, p_dst);
     }
     p_overlay->status = Displayed;