Split the 'background and settings' panel in 3d window in 2 parts.

Instructions for how to add panels there:

- add a handler define code in BIF_space.h
- create a menu item that invokes a add_blockhandler()
- add to view3d_blockhandlers() the correct handler for it

- plus create a panel itself, just copy one... it needs some stuff
  to get working, docs for that are for later

source/blender/include/BIF_space.h

@@ -51,9 +51,8 @@ struct BWinEvent;
 
 /* view3d handler codes */
 #define VIEW3D_HANDLER_BACKGROUND	1
-#define VIEW3D_HANDLER_VIEW			2
+#define VIEW3D_HANDLER_PROPERTIES	2
 #define VIEW3D_HANDLER_OBJECT		3
-#define VIEW3D_HANDLER_VERTEX		4
 
 /* ipo handler codes */
 #define IPO_HANDLER_SETTINGS	20