Android: Make old manifests work on Android 5

On newer Androids, exceptions have started happening when using old
manifests that refer to splash.xml because the layout is missing
some required attributes. We add these to avoid crashing with these
apps.

Change-Id: Iefd4718e811df844e53890ee5bc772871d0a9803
Task-number: QTBUG-42807
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>

src/android/java/res/layout/splash.xml

 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" />
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="fill_parent"
+    android:layout_height="fill_parent" />