extern int dns_lookup(dns_answer *, const uschar *, int, const uschar **);
extern void dns_pattern_init(void);
extern int dns_special_lookup(dns_answer *, const uschar *, int, const uschar **);
-extern dns_record *dns_next_rr(dns_answer *, dns_scan *, int);
+extern dns_record *dns_next_rr(const dns_answer *, dns_scan *, int);
extern uschar *dns_text_type(int);
extern void dscp_list_to_stream(FILE *);
extern BOOL dscp_lookup(const uschar *, int, int *, int *, int *);