Android: Don't use separate thread for MotionAlertDialog

This is an Android continuation of bc95c00. We now call
InputDetector::Update immediately after receiving an input event from
Android instead of periodically calling it in a sleep loop. This
improves detection of very short inputs, which are especially likely to
occur for volume buttons on phones (or at least on my phone) if you
don't intentionally keep them held down.

Source/Android/jni/AndroidCommon/IDCache.h

@@ -112,6 +112,9 @@ jclass GetCoreDeviceControlClass();
 jfieldID GetCoreDeviceControlPointer();
 jmethodID GetCoreDeviceControlConstructor();
 
+jclass GetInputDetectorClass();
+jfieldID GetInputDetectorPointer();
+
 jmethodID GetRunnableRun();
 
 }  // namespace IDCache