Work around tzcode's reliance on signed overflow.

I've mailed the tz list about this, and will switch to whatever upstream
fix comes along as soon as it's available.

Bug: 10310929
Change-Id: I36bf3fcf11f5ac9b88137597bac3487a7bb81b0f

tests/time_test.cpp

@@ -54,3 +54,16 @@ TEST(time, gmtime) {
   ASSERT_EQ(0, broken_down->tm_mon);
   ASSERT_EQ(1970, broken_down->tm_year + 1900);
 }
+
+#ifdef __BIONIC__
+TEST(time, mktime_10310929) {
+  struct tm t;
+  memset(&t, 0, sizeof(tm));
+  t.tm_year = 200;
+  t.tm_mon = 2;
+  t.tm_mday = 10;
+
+  ASSERT_EQ(-1, mktime(&t));
+  ASSERT_EQ(-1, mktime_tz(&t, "UTC"));
+}
+#endif