[Fixes #143] Replace deprecated `twoway` with `memchr`

[michalfita]

The author of twoway marked it as deprecated. This PR replaces it with maintained memchr crate.

[kpcyrd]

Pulling in warp currently causes my project to be flagged with https://osv.dev/RUSTSEC-2021-0146:

╭─────────────────────────────────────┬───────────┬─────────┬─────────┬────────────╮
│ OSV URL (ID IN BOLD)                │ ECOSYSTEM │ PACKAGE │ VERSION │ SOURCE     │
├─────────────────────────────────────┼───────────┼─────────┼─────────┼────────────┤
│ https://osv.dev/RUSTSEC-2021-0145   │ crates.io │ atty    │ 0.2.14  │ Cargo.lock │
│ https://osv.dev/GHSA-wcg3-cvx6-7396 │ crates.io │ time    │ 0.1.45  │ Cargo.lock │
│ https://osv.dev/RUSTSEC-2020-0071   │           │         │         │            │
│ https://osv.dev/RUSTSEC-2021-0146   │ crates.io │ twoway  │ 0.1.8   │ Cargo.lock │
╰─────────────────────────────────────┴───────────┴─────────┴─────────┴────────────╯

This patch would get rid of twoway in my project.

[michalfita]

@rillian Running cargo update ended up with updates that break this code, it doesn't compile any more. I tried more conservative approach, but no luck.

I'm sorry, I don't have time for at least next 9 months to fix @abonander's code into state where this stuff would work again. He has to fix master, remove deprecated stuff and repair the fuzzer with recent released version.

As far as I see things, @abonander abandoned this project over 1½ years ago.

[rillian]

@michalfita thanks for the quick response! You're right, the fuzzer isn't working anyway, so I withdraw my suggestion.

I agree maintainership has been sparse, but it's an important crate for web service applications, so I wanted to do what I could to help things along.