AFAIK, "timelimit" and "timeleft" don't exist in the Half-Life globalvars_t structure. These are variables that are computed out of gpGlobals->time. Let's say timelimit is the date at which the round will end, and timeleft is what it says.
Code:
// on round start
timelimit = gpGlobals->time + CVAR_GET_FLOAT ("mp_thecvarthatholdstheroundduration");
// anytime
timeleft = timelimit - gpGlobals->time;