Disable HIDAPI.

Problem one: it requires its own binary, which we haven't built. There
are instructions in sdl/src/hidapi/README.txt, if we ever want to try.

Problem two: the Android app segfaults when `hid_init()` calls
`g_JVM->AttachCurrentThread()`. This might be a bug in NDK 21's jni.h,
but that seems unlikely. Perhaps a version mismatch?

In any case, we aren't using the code at the moment, so the easy answer
is to leave it out.

templates/android/template/app/src/main/java/org/libsdl/app/SDLActivity.java

@@ -371,7 +371,8 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
 
         mClipboardHandler = new SDLClipboardHandler();
 
-        mHIDDeviceManager = HIDDeviceManager.acquire(this);
+        // TODO: Enable HIDDeviceManager?
+        // mHIDDeviceManager = HIDDeviceManager.acquire(this);
 
         // Set up the surface
         mSurface = new SDLSurface(getApplication());