Export of internal Abseil changes

--
880e4ea366ff27f2b5b0c2f693f05424a1e47fbf by Derek Mauro <dmauro@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 325351285
GitOrigin-RevId: 880e4ea366ff27f2b5b0c2f693f05424a1e47fbf
Change-Id: I9003e713eff7315f4d38ca5c88efe6151bc26ac4

absl/time/internal/cctz/src/time_zone_libc.cc

@@ -153,7 +153,8 @@ std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) {
   std::tm tm;
   while (lo + 1 != hi) {
     const std::time_t mid = lo + (hi - lo) / 2;
-    if (std::tm* tmp = local_time(&mid, &tm)) {
+    std::tm* tmp = local_time(&mid, &tm);
+    if (tmp != nullptr) {
       if (tm_gmtoff(*tmp) == offset) {
         hi = mid;
       } else {
@@ -163,7 +164,8 @@ std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) {
       // If std::tm cannot hold some result we resort to a linear search,
       // ignoring all failed conversions.  Slow, but never really happens.
       while (++lo != hi) {
-        if (std::tm* tmp = local_time(&lo, &tm)) {
+        tmp = local_time(&lo, &tm);
+        if (tmp != nullptr) {
           if (tm_gmtoff(*tmp) == offset) break;
         }
       }

absl/time/internal/cctz/src/time_zone_lookup_test.cc

@@ -1004,13 +1004,13 @@ TEST(MakeTime, SysSecondsLimits) {
 #if defined(_WIN32) || defined(_WIN64)
     // localtime_s() and gmtime_s() don't believe in years outside [1970:3000].
 #else
-    const time_zone utc = LoadZone("libc:UTC");
+    const time_zone cut = LoadZone("libc:UTC");
     const year_t max_tm_year = year_t{std::numeric_limits<int>::max()} + 1900;
-    tp = convert(civil_second(max_tm_year, 12, 31, 23, 59, 59), utc);
+    tp = convert(civil_second(max_tm_year, 12, 31, 23, 59, 59), cut);
-    EXPECT_EQ("2147485547-12-31T23:59:59+00:00", format(RFC3339, tp, utc));
+    EXPECT_EQ("2147485547-12-31T23:59:59+00:00", format(RFC3339, tp, cut));
     const year_t min_tm_year = year_t{std::numeric_limits<int>::min()} + 1900;
-    tp = convert(civil_second(min_tm_year, 1, 1, 0, 0, 0), utc);
+    tp = convert(civil_second(min_tm_year, 1, 1, 0, 0, 0), cut);
-    EXPECT_EQ("-2147481748-01-01T00:00:00+00:00", format(RFC3339, tp, utc));
+    EXPECT_EQ("-2147481748-01-01T00:00:00+00:00", format(RFC3339, tp, cut));
 #endif
   }
 }