Rework MonitorId::get_native_identifier (#267)

* Rework MonitorId::get_native_identifier

* Try fix compilation

* Returns the monitor ID on wayland as well

* Try fix compilation

* Fix iOS compilation

src/os/windows.rs

@@ -1,6 +1,7 @@
 #![cfg(target_os = "windows")]
 
 use libc;
+use MonitorId;
 use Window;
 use WindowBuilder;
 use winapi;
@@ -35,3 +36,16 @@ impl WindowBuilderExt for WindowBuilder {
         self
     }
 }
+
+/// Additional methods on `MonitorId` that are specific to Windows.
+pub trait MonitorIdExt {
+    /// Returns the name of the monitor specific to the Win32 API.
+    fn native_id(&self) -> String;
+}
+
+impl MonitorIdExt for MonitorId {
+    #[inline]
+    fn native_id(&self) -> String {
+        self.inner.get_native_identifier()
+    }
+}