Fixed Android build error on older SDK

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

@@ -217,7 +217,7 @@ public class SDLActivity extends Activity {
          * window for Android UI purposes, as a result.
          */
         int iFlags = 
-            View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY |
+            //View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY | // Only available since API 19
             View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |
             View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
             View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |