phf-generator - tests fail with criterion feature.

[plugwash]

While working on updating the rust phf packages in Debian I discovered that the phf_generator crate fails to build when the criterion feature is enabled. I bisected this to 6d5bfb4 "update to rand 0.8".

Anyway, fixing the code I found two problems. The first is that the "Alphanumeric" distribution now returns u8 rather than char. The second is that "generate_hash" only accepts strings if the "std" feature in phf_shared is enabled.

I fixed the first by adding a ".map(char::from)" and the second by making the criterion feature in phf_generator depend on the std feature is phf_shared

The patch I intend to upload to Debian is at https://salsa.debian.org/rust-team/debcargo-conf/-/blob/master/src/phf-generator/debian/patches/fix-criterion-feature.patch