* Factor redundant code in std/crypto/chacha20
* Add support for XChaCha20, and the XChaCha20-Poly1305 construction.
XChaCha20 is a 24-byte version of ChaCha20, is widely implemented
and is on the standards track:
https://tools.ietf.org/html/draft-irtf-cfrg-xchacha-03
* Add support for encryption/decryption with the authentication tag
detached from the ciphertext
* Add wrappers with an API similar to the Gimli AEAD type, so that
we can use and benchmark AEADs with a common API.
* `std.mem.Compare` is now `std.math.Order` and the enum tags
renamed to follow new style convention.
* `std.mem.compare` is renamed to `std.mem.order`.
* new function `std.math.order`
* Implements #3768. This is a sweeping breaking change that requires
many (trivial) edits to Zig source code. Array values no longer
coerced to slices; however one may use `&` to obtain a reference to
an array value, which may then be coerced to a slice.
* Adds `IrInstruction::dump`, for debugging purposes. It's useful to
call to inspect the instruction when debugging Zig IR.
* Fixes bugs with result location semantics. See the new behavior test
cases, and compile error test cases.
* Fixes bugs with `@typeInfo` not properly resolving const values.
* Behavior tests are passing but std lib tests are not yet. There
is more work to do before merging this branch.
