thrd_equal
int thrd_equal(thrd_t, thrd_t);
ATF_REQUIRE(thrd_equal(s, s) != 0);
ATF_REQUIRE(thrd_equal(t, s) == 0);
ATF_REQUIRE(thrd_equal(s, t) == 0);
ATF_REQUIRE(thrd_equal(t, t) != 0);