We should probably restore this in the future, but we need to rethink
how we fuzz hashes -- right now when cfg(fuzzing) is set, we break all
the hash functions in a way that won't match any other library.
We should probably make this breakage opt-in but this will require
buy-in from rust-lightning and maybe others.
AFAICT we literally never used this; it was available only on the
bitcoin targets and not the honggfuzz ones; AFL has a broken dep
tree (or at least, requires some more MSRV pins that I did not care
to investigate).
Just remove it entirely.
Andrew Poelstra