Android: Fixed compile warning about a missing prototype (thanks, Sylvain!).

Fixes Bugzilla #3351.

src/main/android/SDL_android_main.c

@@ -16,6 +16,9 @@
 /* Called before SDL_main() to initialize JNI bindings in SDL library */
 extern void SDL_Android_Init(JNIEnv* env, jclass cls);
 
+/* This prototype is needed to prevent a warning about the missing prototype for global function below */
+JNIEXPORT int JNICALL Java_org_libsdl_app_SDLActivity_nativeInit(JNIEnv* env, jclass cls, jobject array);
+
 /* Start up the SDL app */
 JNIEXPORT int JNICALL Java_org_libsdl_app_SDLActivity_nativeInit(JNIEnv* env, jclass cls, jobject array)
 {