Merge "Update doc wrt to android:debuggable and CheckJNI"

<pre>D Late-enabling CheckJNI</pre>

<p>You can also set the <code>android:debuggable</code> attribute in your application's manifest to

turn on CheckJNI just for your app. Note that the Android build tools will do this automatically for

certain build types.

<a name="native_libraries" id="native_libraries"></a>