Updates to the NTLMSSP code again - moving the base64 decode fuctionality out

Updates to the NTLMSSP code again - moving the base64 decode fuctionality out
of the SWAT code, and adding a base64 encoder.

The main purpose of this patch is to add NTLMSSP support to 'ntlm_auth', for
use with Squid.  Unfortunetly the squid side doesn't quite support what we need
yet.

Changes to winbind to get us the info we need, and a couple of consequential
changes/cleanups in the rest of the code.

Andrew Bartlett