Update vmihailenco/msgpack to v5

[oleggator]

Breaking change

Now msgpack encoded integers decodes to corresponding Golang integer type.
It's the behaviour of the new version of vmihailenco/msgpack library.

For example:
before: int8 msgpack encoded integer decodes to int64 Golang variable
now: int8 msgpack encoded integer decodes to int8 Golang variable

[funny-falcon]

First, it is breaking change, therefore it could not be merged before V2.
Second, I HATE THIS CHANGE in vmichailenco/msgpack. It is most stupid thing he could make with his library, and he did it indeed. This main thing I don't want to mess with newer versions of vmichailenco/msgpack and wish to replace it with something different.

[FZambia]

before: int8 msgpack encoded integer decodes to int64 Golang variable
now: int8 msgpack encoded integer decodes to int8 Golang variable

decoder.UseLooseInterfaceDecoding(true) should help I suppose?

[funny-falcon]

@FZambia hmm... looks promising.

[oleggator]

Good idea.
But the behaviour still different from v2. In v5 fixed numbers decodes to int64, but in v2 positive fixed numbers decodes to uint64.

[FZambia]

Yeah, this is still a breaking change... But maybe this can help staying with vmihailenco/msgpack in go-tarantool next major release.

[ernado]

We need msgpack.RawMessage support and going to maintain internal fork until this is merged.

[Totktonada]

This work is continued in PR #174.