SAM database "set user info".

SAM database "set user info".
----------------------------

- removed DOM_RID4

- removed SAMR_UNKNOWN_32

- added SAMR_SET_USERINFO (opcode 0x32)

- added level 0x1 to SAMR_QUERY_DOM_INFO (needed for create user)

- fixed pwdb_gethexpwd() it was failing on XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

- added mod_sam21pwd_entry()

- preparing to call mod_sam21pwd_entry()

- added "user session key" to user_struct.dc.  this is md4(nt#) and is
  needed to decode user's clear-text passwords in SAMR_SET_USERINFO.

- split code out in chgpasswd.c to decode 516 byte password buffers.
(This used to be commit 2e58ed742435befe419aa366c4052019fede8c23)