Updated to version 3.1.5 for development

We should bump the version immediately before and after release so the release version corresponds to a fixed snapshot of code.

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

@@ -60,7 +60,7 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
     private static final String TAG = "SDL";
     private static final int SDL_MAJOR_VERSION = 3;
     private static final int SDL_MINOR_VERSION = 1;
-    private static final int SDL_MICRO_VERSION = 3;
+    private static final int SDL_MICRO_VERSION = 5;
 /*
     // Display InputType.SOURCE/CLASS of events and devices
     //