Add message to RS docs about application vs. library packaging.

Change-Id: I49b694629ded066e5ee9c1af29970c59cb637fdd

docs/html/guide/topics/renderscript/compute.jd

@@ -56,7 +56,9 @@ contain:</p>
 RenderScript kernel language used in this script. Currently, 1 is the only valid value.</li>
 
 <li>A pragma declaration (<code>#pragma rs java_package_name(com.example.app)</code>) that
-declares the package name of the Java classes reflected from this script.</li>
+declares the package name of the Java classes reflected from this script.
+Note that your .rs file must be part of your application package, and not in a
+library project.</li>
 
 <li>Some number of invokable functions. An invokable function is a single-threaded RenderScript
 function that you can call from your Java code with arbitrary arguments. These are often useful for
@@ -308,4 +310,4 @@ function launches as necessary.</li>
 <li><strong>Tear down the RenderScript context.</strong> The RenderScript context can be destroyed
 with {@link android.renderscript.RenderScript#destroy} or by allowing the RenderScript context
 object to be garbage collected. This will cause any further use of any object belonging to that
-context to throw an exception.</li> </ol>
+context to throw an exception.</li> </ol>