1. The most part of this patch changed the unknown_3 flag to the now known

1. The most part of this patch changed the unknown_3 flag to the now known
meaning of fields_present bit mask. Also avoid it being saved in backends (0
is saved where removing the unit32 would have produced a format change).
Also add support in samr functions to correctly interpret the flags.
Flags still not set properly (eg. still set all flags 0xffffff as previous
code), need a tool to test this properly (I',ve done preliminary tests with
samba4 rpc torture and it seem to work properly against w2k).

2. Patch for handlig the flag user must change password at next logon
in usrmgr based on Jianliang Lu <j.lu@tiesse.com> patch