Rollup merge of rust-lang#57740 - JakubOnderka:ipv4addr-to_ne_bytes, …

…r=scottmcm

Use `to_ne_bytes` for converting IPv4Addr to octets

It is easier and it should be also faster, because [`to_ne_bytes`](https://doc.rust-lang.org/std/primitive.u32.html#method.to_ne_bytes) just calls `mem::transmute`.

src/libstd/net/ip.rs

@@ -392,8 +392,7 @@ impl Ipv4Addr {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn octets(&self) -> [u8; 4] {
-        let bits = u32::from_be(self.inner.s_addr);
-        [(bits >> 24) as u8, (bits >> 16) as u8, (bits >> 8) as u8, bits as u8]
+        self.inner.s_addr.to_ne_bytes()
     }
 
     /// Returns [`true`] for the special 'unspecified' address (0.0.0.0).