Add an Ant build rule

In order to avoid having to check out a large portion of the Android
framework, allow Volley to be self-contained (and built using the
existing Android application build system).

Change-Id: I45a23b98a2008ad707532da31f1e9b75c7071c25
diff --git a/project.properties b/project.properties
index 730e911..28341e2 100644
--- a/project.properties
+++ b/project.properties
@@ -9,3 +9,7 @@
 
 # Project target.
 target=android-14
+
+# Make sure to pass a valid value to renderscript
+# https://code.google.com/p/android/issues/detail?id=40487
+renderscript.opt.level=O0