Fix possible integer overflow in mp_check()

Malformed MessagePack can cause `int k` counter overflow
inside mp_check()/mp_next().

See https://github.com/tarantool/nginx_upstream_module/issues/79
See https://github.com/rtsisyk/msgpuck/issues/16
Closes #2540

msgpuck @ 40e24ccf

-Subproject commit 2598bce249077ca49ba311247e03b2a10558bbbb
+Subproject commit 40e24ccf3ec191e6f576da967a64630ca2160bfc

test/unit/msgpack.result

-1..19
+1..20
     1..135
     # *** test_uints ***
     # uint 0U
@@ -1816,3 +1816,11 @@ ok 18 - subtests
     ok 96 - mp_read_double(mp_encode_strl(100)) check pos unchanged
     # *** test_numbers: done ***
 ok 19 - subtests
+    1..4
+    # *** test_overflow ***
+    ok 1 - mp_check array overflow
+    ok 2 - mp_check map overflow
+    ok 3 - mp_check str overflow
+    ok 4 - mp_check bin overflow
+    # *** test_overflow: done ***
+ok 20 - subtests