Make the iterators slightly better

* Implement some useful traits on them.
* Make reference an into-iterator.

src/ipv4.rs

@@ -253,6 +253,7 @@ impl From<Ipv4Addr> for Ipv4Network {
     }
 }
 
+#[derive(Clone, Debug)]
 pub struct Ipv4NetworkIterator {
     next: u32,
     end: u32,
@@ -272,6 +273,14 @@ impl Iterator for Ipv4NetworkIterator {
     }
 }
 
+impl IntoIterator for &'_ Ipv4Network {
+    type IntoIter = Ipv4NetworkIterator;
+    type Item = Ipv4Addr;
+    fn into_iter(self) -> Ipv4NetworkIterator {
+        self.iter()
+    }
+}
+
 /// Converts a `Ipv4Addr` network mask into a prefix.
 ///
 /// If the mask is invalid this will return an `IpNetworkError::InvalidPrefix`.