rustdoc: "stable since" version is incorrect for std::ffi::CStr

[dzil123]

The documentation page for std::ffi::CStr says it was stabilized in 1.64.0, but it should say 1.0.0.

Applies to latest stable and nightly
https://doc.rust-lang.org/stable/std/ffi/struct.CStr.html
https://doc.rust-lang.org/nightly/std/ffi/struct.CStr.html

This was correct back in 1.61.0
https://doc.rust-lang.org/1.61.0/std/ffi/struct.CStr.html

[steffahn]

The problem is that core::ffi::CStr was stabilized in 1.64, and the path in std has become a re-export.