Resolve "RRset merge operation is too slow for big RRsets"

Closes #518 (closed)

daemon/lua/kres-gen.lua

@@ -126,6 +126,7 @@ struct ranked_rr_array_entry {
 	_Bool yielded : 1;
 	_Bool to_wire : 1;
 	_Bool expiring : 1;
+	_Bool in_progress : 1;
 	knot_rrset_t *rr;
 };
 typedef struct ranked_rr_array_entry ranked_rr_array_entry_t;
@@ -352,6 +353,7 @@ int kr_family_len(int);
 struct sockaddr *kr_straddr_socket(const char *, int, knot_mm_t *);
 int kr_straddr_split(const char *, char * restrict, uint16_t *);
 int kr_ranked_rrarray_add(ranked_rr_array_t *, const knot_rrset_t *, uint8_t, _Bool, uint32_t, knot_mm_t *);
+int kr_ranked_rrarray_finalize(ranked_rr_array_t *, uint32_t, knot_mm_t *);
 void kr_qflags_set(struct kr_qflags *, struct kr_qflags);
 void kr_qflags_clear(struct kr_qflags *, struct kr_qflags);
 int kr_zonecut_add(struct kr_zonecut *, const knot_dname_t *, const void *, int);