This patch modifies 'net rpc vampire' to add new and existing users to both

This patch modifies 'net rpc vampire' to add new and existing users to both
the idmap and the SAM.

The basic idea is this:  Lookup the user with GetPwnam(), and if they
exist then use that uid.  This is what people expect.  If the user does
not exist, try and run the right script.

This is also what people expect from previous Samba 3.0 behaviour, where
the Get_Pwnam() was at runtime.

If the idmap entry for this SID isn't valid, or isn't the right value,
modify the idmap to account for this mapping.

Also, the same logic is applied to the primary gid - if it has changed,
update the user's primary unix group.

This patch allows users to be added without a mapping - this is fine for
machine accounts, for example.  I've given it a quick test against my
Win2k DC, and I *think* it's sane.

Andrew Bartlett