fixed pocoproject#318: Logger local time doesn't automatically accoun…

…t for DST

Foundation/src/Timezone_UNIX.cpp

@@ -16,6 +16,7 @@
 
 #include "Poco/Timezone.h"
 #include "Poco/Exception.h"
+#include "Poco/Mutex.h"
 #include <ctime>
 
 
@@ -32,23 +33,33 @@ class TZInfo
 
 	int timeZone()
 	{
+		Poco::FastMutex::ScopedLock lock(_mutex);
+
 	#if defined(__APPLE__)  || defined(__FreeBSD__) || defined (__OpenBSD__) || defined(POCO_ANDROID) // no timezone global var
 		std::time_t now = std::time(NULL);
 		struct std::tm t;
 		gmtime_r(&now, &t);
 		std::time_t utc = std::mktime(&t);
 		return now - utc;
 	#elif defined(__CYGWIN__)
+		tzset();
 		return -_timezone;
 	#else
+		tzset();
 		return -timezone;
 	#endif
 	}
 
 	const char* name(bool dst)
 	{
+		Poco::FastMutex::ScopedLock lock(_mutex);
+
+		tzset();		
 		return tzname[dst ? 1 : 0];
 	}
+
+private:
+	Poco::FastMutex _mutex;
 };