specify strict APP_PLATFORM to avoid crashes on devices with older android version

src/ui/android/AndroidManifest.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.grammaticalframework.ui.android"
-    android:versionCode="7"
+    android:versionCode="9"
     android:versionName="1.2"
     android:installLocation="auto" >
 

src/ui/android/jni/Application.mk

@@ -1,2 +1,2 @@
-
+APP_PLATFORM := android-8
 APP_CFLAGS := -std=gnu99