Add CleanSpec.mk to frameworks/rs and add support for building all tests.

Without the tests/Android.mk, each test would need to be individually built
using mm in the separate directories. I also added a CleanSpec.mk to properly
get rid of all the stale build-related files from the moved tests.

Change-Id: I248d6f1252b3b6e02874917194c5e8233e70edef
diff --git a/java/tests/Android.mk b/java/tests/Android.mk
new file mode 100644
index 0000000..5053e7d
--- /dev/null
+++ b/java/tests/Android.mk
@@ -0,0 +1 @@
+include $(call all-subdir-makefiles)