extern BOOL readconf_depends(driver_instance *, uschar *);
extern void readconf_driver_init(uschar *, driver_instance **,
driver_info *, int, void *, int, optionlist *, int);
-extern uschar *readconf_find_option(void *);
+extern const uschar *readconf_find_option(void *);
extern void readconf_main(BOOL);
extern void readconf_options_from_list(optionlist *, unsigned, const uschar *, uschar *);
extern BOOL readconf_print(const uschar *, const uschar *, BOOL);