added: TimeZone struct (core)

this class has information about a time zone (utf offset, daylight saving time)
       and methods for converting between UTC and local time
       structs User and Config has a TimeZone object
       System::ToLocal() and System::ToUTC() uses it for converting
       (depending whether a user is logged or not)


git-svn-id: svn://ttmath.org/publicrep/winix/trunk@842 e52654a7-88a9-db11-a3e9-0013d4bc506e

core/users.cpp

@@ -47,15 +47,6 @@ void Users::ReadUsers(Db * db)
 }
 
 
-void Users::SetTimeZoneOffset(int offset)
-{
-	Table::Iterator i;
-
-	for(i=table.Begin() ; i!=table.End() ; ++i)
-	{
-		i->time_zone_offset = offset;
-	}
-}
 
 
 bool Users::AddUser(const User & user)