patch to Samba4 for Win7-beta domain join

[tridge at samba.org]

Hi Andrew,

As we discussed on IRC, I've pushed a patch
(fe5b0b595c926aea0916541ceeaf610bc018cb63) to s4 that allows a domain
join from Win7-beta to work. The patch involves two parts:

 - a small change to fix the dcesrv_netr_DsRGetDCNameEx2 code to cope
   with short domain names, and fix the bogus use of the dnsDomain
   attribute

 - a hack in password_hash.c to enable setting of machine account
   passwords via a unicodePwd LDAP modify

The unicodePwd hack is the interesting one. As the commit says:

    This patch copes with the ldap unicodePwd modify by recognising the
    format and creating the correct attributes on the fly. Note that this
    assumes we will never get a unicodePwd attribute set in NT MD4 format
    with the first 2 and last 2 bytes set to 0x22 0x00.

    Andrew Bartlett is looking at a more robust solution, possibly using a
    flag to say that this modify came via ldap, and not internal ldb
    calls.

What do you think of this as a temporary solution?

Cheers, Tridge