Adding undo flag to the python run flag operator.

It's safer this way.

source/blender/editors/space_script/script_edit.c

@@ -81,6 +81,7 @@ void SCRIPT_OT_python_file_run(wmOperatorType *ot)
 	ot->name= "Run python file";
 	ot->description= "Run Python file.";
 	ot->idname= "SCRIPT_OT_python_file_run";
+	ot->flag = OPTYPE_UNDO;
 
 	/* api callbacks */
 	ot->exec= run_pyfile_exec;