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/session.h

@@ -53,14 +53,6 @@ struct Session
 	// (used to calculate spam)
 	time_t last_time_get;
 	
-	// how many seconds should be added/substructed from the universal time
-	// to create the local time for this session/user
-	// it has combined time zone offset and daylight saving time
-	// so when reading a value from a user (e.g. in html form) you should
-	// substract tz_add and when printing you should add it
-	time_t tz_add;
-
-
 
 	// 0 - means that nobody is logged	
 	User * puser;