Archives that want to hedge against a SHA-2 break need clients that
already understand a different hash family. Update libapt-pkg to include
SHA3-256 and SHA3-512 so Release, Packages, and Sources entries using
them are parsed and verified, using the SHA3 digests OpenSSL provides
since 1.1.1.
The new types are first in the preference order. For archives that
publish both families, by-hash requests go to the SHA3 directory,
falling back to the plain path if it is missing.
The tagfile keys are appended after the ABI marker. The exported symbol
set of libapt-pkg is unchanged.
Gianpiero Carpinelli
8b4f0bbec3