cope with openbsd ancient nameser.h

Index: res/res_rtp_asterisk.c
--- res/res_rtp_asterisk.c.orig
+++ res/res_rtp_asterisk.c
@@ -9638,7 +9638,7 @@ static int store_stunaddr_resolved(const struct ast_dn
 		const unsigned char *data = (unsigned char *)ast_dns_record_get_data(record);
 		const int rr_type = ast_dns_record_get_rr_type(record);
 
-		if (rr_type == ns_t_a && data_size == 4) {
+		if (rr_type == T_A && data_size == 4) {
 			ast_rwlock_wrlock(&stunaddr_lock);
 			memcpy(&stunaddr.sin_addr, data, data_size);
 			stunaddr.sin_family = AF_INET;
