Fix p_test_fail()'s va_list abuse.

p_test_fail() was passing a va_list to two separate functions with the
expectation that no reset would occur.  Refactor p_test_fail()'s callers
to instead format two strings and pass them to p_test_fail().

Add a missing parameter to an assert_u64_eq() call, which the compiler
warned about after the assertion macro refactoring.

test/unit/SFMT.c

@@ -1576,7 +1576,7 @@ TEST_BEGIN(test_by_array_64)
 	for (i = 0; i < BLOCK_SIZE64; i++) {
 		if (i < COUNT_1) {
 			assert_u64_eq(array64[i], init_by_array_64_expected[i],
-			    "Output mismatch for i=%d");
+			    "Output mismatch for i=%d", i);
 		}
 		r = gen_rand64(ctx);
 		assert_u64_eq(r, array64[i],