Fix unit test.

Looks like we forgot to update unit tests when we switched from 32-bit to
64-bit ints while tweaking 7cd53b7.

src/test/test_util.c

@@ -4663,7 +4663,7 @@ test_util_laplace(void *arg)
    * array([         -inf,  -80.47189562,  -34.65735903,    0.        ,
    *          34.65735903,   80.47189562,  195.60115027])
    */
-  tt_assert(LONG_MIN + 20 ==
+  tt_assert(LLONG_MIN + 20 ==
             add_laplace_noise(20, 0.0, delta_f, epsilon));
   tt_assert(-60 == add_laplace_noise(20, 0.1, delta_f, epsilon));
   tt_assert(-14 == add_laplace_noise(20, 0.25, delta_f, epsilon));