Blueprint incremental-rehash: post-merge fixes.

Fix a bug in next slot calculation (creeped in with
code review fixes).

include/mhash.h

@@ -131,10 +131,10 @@ void _mh(dump)(struct _mh(t) *h);
 #define put_slot(h, key) _mh(put_slot)(h, key)
 
 static inline mh_int_t
-_mh(next_slot)(mh_int_t link, mh_int_t inc, mh_int_t size)
+_mh(next_slot)(mh_int_t slot, mh_int_t inc, mh_int_t size)
 {
-	link += inc;
-	return link > size ? link - size : link;
+	slot += inc;
+	return slot >= size ? slot - size : slot;
 }
 
 static inline mh_int_t

test/box_big/sql.result

@@ -340,9 +340,9 @@ insert into t4 values(3, 'Creature')
 Insert OK, 1 row affected
 lua for k, v in box.space[4]:pairs() do print(v) end
 ---
+3: {'Creature'}
 1: {'Aardvark'}
 2: {'Bilimbi'}
-3: {'Creature'}
 ...
 lua box.space[4].index[0].idx:min()
 ---