Add support for generating dummy DeviceIDs and WindowIDs (#738)

* Add support for generating dummy DeviceIDs and WindowIDs

* Fix linux

* Improve docs and move dummy to unsafe

* Strengthen guarantees a bit

* Add backticks to CHANGELOG.md

Co-Authored-By: Xaeroxe <xaeroxe@amethyst-engine.org>

src/platform/android/mod.rs

@@ -170,9 +170,21 @@ impl EventsLoopProxy {
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct WindowId;
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId;
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId
+    }
+}
+
 pub struct Window {
     native_window: *const c_void,
 }