breaking: Remove FromRawFd/Handle implementations

This is a breaking change, but I think it's justified for two reasons:

- It removes all unsafe code from this crate.
- FromRawFd is superseded by From<OwnedFd>

cc rust-secure-code/safety-dance#83

Signed-off-by: John Nunley <dev@notgull.net>

src/lib.rs

@@ -23,6 +23,7 @@
 //! # std::io::Result::Ok(()) });
 //! ```
 
+#![forbid(unsafe_code)]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
 #![doc(
     html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
@@ -1070,20 +1071,6 @@ impl From<std::fs::File> for File {
     }
 }
 
-#[cfg(unix)]
-impl std::os::unix::io::FromRawFd for File {
-    unsafe fn from_raw_fd(raw: std::os::unix::io::RawFd) -> File {
-        File::from(std::fs::File::from_raw_fd(raw))
-    }
-}
-
-#[cfg(windows)]
-impl std::os::windows::io::FromRawHandle for File {
-    unsafe fn from_raw_handle(raw: std::os::windows::io::RawHandle) -> File {
-        File::from(std::fs::File::from_raw_handle(raw))
-    }
-}
-
 #[cfg(unix)]
 impl std::os::unix::io::AsRawFd for File {
     fn as_raw_fd(&self) -> std::os::unix::io::RawFd {