Add scrypt unit tests

Make sure our scrypt library is passing the test vectors provided at:
http://tools.ietf.org/html/draft-josefsson-scrypt-kdf-00#page-11

This will allow us to substitute in new Salsa20/8, PBKDF2, etc
implementations that are faster without breaking compatibility.

Change-Id: I89024b637e0075e5018526e4147148e6fc8e4d96
diff --git a/Android.mk b/Android.mk
index 4920d2d..7fa96d0 100644
--- a/Android.mk
+++ b/Android.mk
@@ -9,3 +9,5 @@
 # that import_openssl.sh import won't remove them.
 include $(LOCAL_PATH)/build-config.mk
 include $(LOCAL_PATH)/Scrypt.mk
+
+include $(call all-named-subdir-makefiles,tests)