Ignore GCC warnings.

* 4.9 missing initializer warnings
* pedantic for __int128 case
* Wrap diagnostic push and pop in tz.cpp and date.h.

tz.cpp

@@ -141,6 +141,12 @@ static CONSTDATA char folder_delimiter = '/';
 
 #endif
 
+#if __GNUC__ < 5
+// GCC 4.9 Bug 61489 Wrong warning with -Wmissing-field-initializers
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wmissing-field-initializers"
+#endif
+
 #ifdef _WIN32
 
 namespace
@@ -3100,12 +3106,6 @@ current_zone()
 
 #else // !WIN32
 
-#ifdef __GNUC__
-// GCC complains about unused return from strerror_r
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wunused-result"
-#endif
-
 const time_zone*
 current_zone()
 {
@@ -3183,10 +3183,6 @@ current_zone()
     throw std::runtime_error("Could not get current timezone");
 }
 
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif
-
 #endif // !WIN32
 
 #if defined(TZ_TEST) && defined(TIMEZONE_MAPPING)
@@ -3208,4 +3204,9 @@ locate_native_zone(const std::string& native_tz_name)
 
 #endif  // TZ_TEST && TIMEZONE_MAPPING
 
+
 }  // namespace date
+
+#if __GNUC__ < 5
+# pragma GCC diagnostic pop
+#endif