7a7ca8238f
implement zeroed and uninitialized with MaybeUninit This is the second attempt of doing such a change (first PR: https://github.com/rust-lang/rust/pull/62150). The last change [got reverted](https://github.com/rust-lang/rust/pull/63343) because it [caused](https://github.com/rust-lang/rust/issues/62825) some [issues](https://github.com/rust-lang/rust/issues/52898#issuecomment-512182438) in [code that incorrectly used these functions](https://github.com/erlepereira/x11-rs/issues/99). Since then, the [problematic code has been fixed](https://github.com/erlepereira/x11-rs/pull/101), and rustc [gained a lint](https://github.com/rust-lang/rust/pull/63346) that is able to detect many misuses of these functions statically and a [dynamic check that panics](https://github.com/rust-lang/rust/pull/66059) instead of causing UB for some incorrect uses. Fixes https://github.com/rust-lang/rust/issues/62825