Remove memoffset dependency.

[aDotInTheVoid]

std::mem::offset has been availible on stable since 1.77.0. memoffset uses this when compiled against a recent enough rustc.

Moving to the implementation in std lets me drop both memoffset and autocfg from my transitive dependencies.

[lnicola]

Since we're here, we should probably add a rust-version key. You can ignore the CI error, it's a false positive.

[Veykril]

And bump the version number in the Cargo.toml so CI does a release

[aDotInTheVoid]

@Veykril do you want a minor or patch release? this crate doesn't have an MSRV policy.

[Veykril]

Patch should be fine, I don't see any breaking changes isnce the last bump

[aDotInTheVoid]

Done

[Veykril]

Thanks!

[aDotInTheVoid]

Gah, the autopublish doesn't work due to false positives in invalid_reference_casting. They're fixed on nightly, but not beta (but are backport nominated). I don't need this on crates.io anytime soon, so I'm happy to wait for CI to become unborked, but it'll probably require a manual CI rerun of the specific commit (if you want v0.15.16 to correspond to that commit)