fix for 2 segfaults running in background mode.

- operators which reload G.main would crash blender if called from python and then accessed bpy.data.*
- WM_read_homefile_exec was setting the contexts Scene to NULL as a signal for the event system, this didnt work in background mode, crashing when property update functions expected scene to be set.

source/blender/python/intern/bpy_rna.c

@@ -5316,8 +5316,6 @@ static int bpy_class_validate(PointerRNA *dummyptr, void *py_data, int *have_fun
 	return 0;
 }
 
-extern void BPY_modules_update(bContext *C); //XXX temp solution
-
 /* TODO - multiple return values like with rna functions */
 static int bpy_class_call(bContext *C, PointerRNA *ptr, FunctionRNA *func, ParameterList *parms)
 {