the nt blob ends with 4 zero bytes, this is not the same as
the EOL av-pair terminator!
this makes ntlmv2 work with windows xp with LmCompatibityLevel = 3
tm2sec() ignores tm.tzoff and will use the local timezone for
conversion. to make it work right, we convert the dos timestamp
as GMT and then correct timezone with the offset provided by the
server.
