[Android] Fixes Bug 2041 - can't get SDL_QUIT event...

Thanks to Denis Bernard!

Also, changed the Android manifest so the app doesn't quit with orientation
changes, and made testgles.c exit properly on Android.

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

@@ -121,13 +121,13 @@ public class SDLActivity extends Activity {
         SDLActivity.nativeQuit();
 
         // Now wait for the SDL thread to quit
-        if (mSDLThread != null) {
+        if (SDLActivity.mSDLThread != null) {
             try {
-                mSDLThread.join();
+                SDLActivity.mSDLThread.join();
             } catch(Exception e) {
                 Log.v("SDL", "Problem stopping thread: " + e);
             }
-            mSDLThread = null;
+            SDLActivity.mSDLThread = null;
 
             //Log.v("SDL", "Finished waiting for SDL thread");
         }