This reverts commit 0c99ba1eab, reversing
changes made to 5f92b070bf.
This caused a CI failure when it landed in master branch due to a
128-bit `@byteSwap` in std.mem.
The HKDF extract function uses HMAC under the hood, but requiring
applications to directly use HMAC functions reduces clarity and
feels like the wrong abstraction.
So, in order to get the PRK length, add a `prk_length` constant
that applications can use directly.
Also add an `extractInit()` function for cases where the keying
material has to be provided as multiple chunks.
We already have a LICENSE file that covers the Zig Standard Library. We
no longer need to remind everyone that the license is MIT in every single
file.
Previously this was introduced to clarify the situation for a fork of
Zig that made Zig's LICENSE file harder to find, and replaced it with
their own license that required annual payments to their company.
However that fork now appears to be dead. So there is no need to
reinforce the copyright notice in every single file.
