New varint with unique values

[ivan386]

In the old code, they have the same value (0)
In the new code, they have:

varint [0] = 0
varint [128 0] = 128
varint [128 128 0] = 16512

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please let us know the company's name.

[dsnet]

The new logic is handling varints incorrectly. I'm not sure what this is trying to achieve.

The binary.PutUvarint function uses the same varint encoding as protos:

	var arr [10]byte
	b := arr[:binary.PutUvarint(arr[:], 16512)]
	fmt.Println(b) // [128 129 1]

Its output disagrees with what your change does.

[ivan386]

Maybe I chose the wrong place for my proposal. This is new more compact varint. All it values is unique. MSB now used in value calc.

Maybe need to add it as new functions DecodeCompactVarint and EncodeCompactVarint.

[dsnet]

This is the wrong place for this. Please submit wire format encoding proposals to the issue tracker at github.com/google/protobuf.

[ivan386]

Done: protocolbuffers/protobuf#4376