Upgrade to the current NetBSD rand implementation.

Also add basic unit tests.

Change-Id: I7fc7ef61d47c1e8fdf8b8eff67a635220c3afd56
diff --git a/tests/Android.mk b/tests/Android.mk
index 38f8ceb..259aced 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -23,6 +23,7 @@
     pthread_test.cpp \
     regex_test.cpp \
     stdio_test.cpp \
+    stdlib_test.cpp \
     string_test.cpp \
     stubs_test.cpp \