recursive from_msgpack implementation will stack overflow

[xgzeng]

from_msgpack function(etc) parses data recursively, which will cause stack overflow when process deep nested structure.
It will be DOS vulnerabilities, if we use library to process data from outside.

Following is example code to generate malicious data. msgpack_pack_array is not shown here.

for (int i = 0; i < 10000; ++i) {
    msgpack_pack_array(buffer, 1);
}
msgpack_pack_array(buffer, 0);

[nlohmann]

The same issue was detected for CBOR in #517.

[xgzeng]

Should we just add a defaut parameter to restrict nesting level?
I think it suits most use case.

[nlohmann]

That would be an effective, yet ugly solution. I would rather have a non-recursive version that uses a stack internally so we can enforce a limit there.

[nlohmann]

Closed in favor of #517.