Normalized message hash

We propose to standardize the normalized external message hash algorithm proposed by Denis Subbotin.

This approach provides a guaranteed ability to find and track a sent message in the TON Blockchain and is particularly useful for tracking pending actions.

Normalization is already supported by Toncenter API, tonscan.org, TON API and tonviewer.com.

Developers are welcome to participate in the discussion:

https://github.com/ton-blockchain/TEPs/pull/467/files?short_path=eec950d#diff-eec950d709a49c0385d78864230b9de72d6003af0be76221a877693730714878