Various post AuthRewrite cleanups, fixups and tidyups.

Various post AuthRewrite cleanups, fixups and tidyups.

Zero out some of the plaintext passwords for paranoia

Fix up some of the other passdb backends with the change to *uid_t rather than
uid_t.

Make some of the code in srv_netlog_nt.c clearer, is passing an array around,
so pass its lenght in is definition, not as a seperate paramater.

Use sizeof() rather than magic numbers, it makes things easier to read.

Cope with a PAM authenticated user who is not in /etc/passwd - currently by
saying NO_SUCH_USER, but this can change in future.

Andrew Bartlett
(This used to be commit 514c91b16baca639bb04638042bf9894d881172a)