Backport some SDL 2.0.16-dev features

- Let Android know that we can handle USB devices
- Support wired Amazon Luna gamepad on Android
- Chromebooks support relative mouse motion now

android-project/app/src/main/AndroidManifest.xml

@@ -60,6 +60,10 @@
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
+            <!-- Let Android know that we can handle some USB devices and should receive this event -->
+            <intent-filter>
+                <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
+            </intent-filter>
             <!-- Drop file event -->
             <!--
             <intent-filter>

android-project/app/src/main/java/org/libsdl/app/HIDDeviceManager.java

@@ -7,6 +7,7 @@ import android.bluetooth.BluetoothAdapter;
 import android.bluetooth.BluetoothDevice;
 import android.bluetooth.BluetoothManager;
 import android.bluetooth.BluetoothProfile;
+import android.os.Build;
 import android.util.Log;
 import android.content.BroadcastReceiver;
 import android.content.Context;
@@ -275,6 +276,7 @@ public class HIDDeviceManager {
             0x15e4, // Numark
             0x162e, // Joytech
             0x1689, // Razer Onza
+            0x1949, // Lab126, Inc.
             0x1bad, // Harmonix
             0x24c6, // PowerA
         };
@@ -382,6 +384,11 @@ public class HIDDeviceManager {
             return;
         }
 
+        if (!mContext.getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE) || (Build.VERSION.SDK_INT < 18)) {
+            Log.d(TAG, "Couldn't initialize Bluetooth, this version of Android does not support Bluetooth LE");
+            return;
+        }
+
         // Find bonded bluetooth controllers and create SteamControllers for them
         mBluetoothManager = (BluetoothManager)mContext.getSystemService(Context.BLUETOOTH_SERVICE);
         if (mBluetoothManager == null) {

android-project/app/src/main/java/org/libsdl/app/SDLActivity.java

@@ -986,11 +986,6 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
      */
     public static boolean supportsRelativeMouse()
     {
-        // ChromeOS doesn't provide relative mouse motion via the Android 7 APIs
-        if (isChromebook()) {
-            return false;
-        }
-
         // DeX mode in Samsung Experience 9.0 and earlier doesn't support relative mice properly under
         // Android 7 APIs, and simply returns no data under Android 8 APIs.
         //