Basic file accessibility checks for Rust.
```rust use std::path::Path; use faccess::{AccessMode, PathExt};
let path = Path::new("/bin/ls");
assert!(path.access(AccessMode::READ | AccessMode::EXECUTE).is_ok()); assert!(path.readable()); assert!(!path.writable()); assert!(path.executable()); ```
On Unix, this uses [faccessat(2)] with AT_EACCESS to check against the
effective user and group ID's.
On Windows it uses, amongst other things, [AccessCheck] to try to match the
appropriate semantics.
On other platforms it simply proxies to exists() and readonly() as appropriate.
Beware not to introduce any serious time-of-check to time-of-use ([TOCTOU]) bugs with these functions. They are strictly best-effort and are absolutely not alternatives to checking to see if opening a file or launching a program actually succeeded.