Core/Thread: Fix race condition converting time values to local time

Replace thread-unsafe localtime() http://www.cplusplus.com/reference/ctime/localtime/ with thread-safe portable ACE_OS::localtime_r() .

Helgrind log:
 Possible data race during read of size 4 at 0x6F183C0 by thread #1
 Locks held: none
  at 0x14E72E3: World::InitDailyQuestResetTime() (World.cpp:2772)
  by 0x14E3A01: World::SetInitialWorldSettings() (World.cpp:1790)
  by 0x101122A: Master::Run() (Master.cpp:164)
  by 0x101740C: main (Main.cpp:142)

 This conflicts with a previous write of size 4 by thread #2
 Locks held: none
  at 0x6C2D3BA: __tzfile_compute (tzfile.c:797)
  by 0x6C2D036: __tz_convert (tzset.c:627)
  by 0x164146C: LogMessage::getTimeStr(long) (Appender.cpp:23)
  by 0x1641550: LogMessage::getTimeStr() (Appender.cpp:31)
  by 0x1641722: Appender::write(LogMessage&) (Appender.cpp:80)
  by 0x1633FCE: Logger::write(LogMessage&) (Logger.cpp:83)
  by 0x16433D8: LogOperation::call() (LogOperation.cpp:29)
  by 0x16428A4: LogWorker::svc() (LogWorker.cpp:45)