Bump the minimum supported Rust version to 1.48.

[sunfishcode]

Would you be willing to bump caps' MSRV to 1.48, so that rust-errno can migrate from winapi to windows-sys?

This isn't urgent, but if it works out, it would eliminate the last winapi dependency for rustix and some of its users, so I figured it's worth asking. windows-sys depends on at least Rust 1.48, so this will require bumping rust-errno's MSRV. caps is one of rust-errno's biggest users.

Last time cap's bumped its MSRV was #46 on 2020-01-09, bumping to Rust 1.36, which was released on 2019-07-04, so it was about 6 months old at that point. Rust 1.48 was released on 2020-11-19, which is about a year and a half old now.

caps is depended on nix with an MSRV of 1.46, however it is only a dev-dependency.

[lucab]

Yes, let's do this. Debian stable is also at 1.48, so I'm doubly-happy with that. Are there semver guidelines for handling MSRV bumps? I haven't been very strict about this so far, and I'd rather keep this to a patch-version bump. Related, there is https://github.com/lucab/caps-rs/pull/78 going on in parallel to remove the errno dependency.

[sunfishcode]

As far as I can tell, there isn't universal consensus on the right way to handle this. I tend to think it can be ok, as long as the new MSRV is still reasonably low, there aren't users known to have lower MSRV needs, and there aren't other practical constraints.

That said, it looks like #78 would be entirely sufficient, so if you want to just do that, that works for me :smile: .

[lucab]

Thanks a lot for the PR, but I merged https://github.com/lucab/caps-rs/pull/78 in the meanwhile.