[dia] win32: add dia_layer_get_extents

[Zander <zbrown src gnome org>]

commit 09b4aebfd093867f90a1392c47a30943d6788e81
Author: Zander Brown <zbrown gnome org>
Date:   Fri Mar 27 13:08:42 2020 +0000

    win32: add dia_layer_get_extents
    
    Fix https://gitlab.gnome.org/GNOME/dia/-/issues/449

 lib/libdia.def | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/lib/libdia.def b/lib/libdia.def
index cd9b6c73..53862255 100644
--- a/lib/libdia.def
+++ b/lib/libdia.def
@@ -584,6 +584,7 @@ EXPORTS
  dia_layer_set_connectable
  dia_layer_get_type
  dia_layer_get_object_list
+ dia_layer_get_extents
 
  line_bbox
  line_line_intersection