feat(raw-fd): implement FromRawFd/FromRawSocket

This allows HttpStream and HttpListener to be created from raw
sockets similar to their Tcp counterparts.  It also fixes up the
signature from i32 to RawFd for the AsRawFd method.

src/net.rs

@@ -172,6 +172,34 @@ impl NetworkListener for HttpListener {
     }
 }
 
+#[cfg(windows)]
+impl ::std::os::windows::io::AsRawSocket for HttpListener {
+    fn as_raw_socket(&self) -> ::std::os::windows::io::RawSocket {
+        self.0.as_raw_socket()
+    }
+}
+
+#[cfg(windows)]
+impl ::std::os::windows::io::FromRawSocket for HttpListener {
+    unsafe fn from_raw_socket(sock: ::std::os::windows::io::RawSocket) -> HttpListener {
+        HttpListener(TcpListener::from_raw_socket(sock))
+    }
+}
+
+#[cfg(unix)]
+impl ::std::os::unix::io::AsRawFd for HttpListener {
+    fn as_raw_fd(&self) -> ::std::os::unix::io::RawFd {
+        self.0.as_raw_fd()
+    }
+}
+
+#[cfg(unix)]
+impl ::std::os::unix::io::FromRawFd for HttpListener {
+    unsafe fn from_raw_fd(fd: ::std::os::unix::io::RawFd) -> HttpListener {
+        HttpListener(TcpListener::from_raw_fd(fd))
+    }
+}
+
 /// A wrapper around a TcpStream.
 pub struct HttpStream(pub TcpStream);
 
@@ -213,13 +241,27 @@ impl ::std::os::windows::io::AsRawSocket for HttpStream {
     }
 }
 
+#[cfg(windows)]
+impl ::std::os::windows::io::FromRawSocket for HttpStream {
+    unsafe fn from_raw_socket(sock: ::std::os::windows::io::RawSocket) -> HttpStream {
+        HttpStream(TcpStream::from_raw_socket(sock))
+    }
+}
+
 #[cfg(unix)]
 impl ::std::os::unix::io::AsRawFd for HttpStream {
-    fn as_raw_fd(&self) -> i32 {
+    fn as_raw_fd(&self) -> ::std::os::unix::io::RawFd {
         self.0.as_raw_fd()
     }
 }
 
+#[cfg(unix)]
+impl ::std::os::unix::io::FromRawFd for HttpStream {
+    unsafe fn from_raw_fd(fd: ::std::os::unix::io::RawFd) -> HttpStream {
+        HttpStream(TcpStream::from_raw_fd(fd))
+    }
+}
+
 impl NetworkStream for HttpStream {
     #[inline]
     fn peer_addr(&mut self) -> io::Result<SocketAddr> {