Various peices of the GSSAPI puzzle.

- Removed GSSAPI functionality from Active Directory since it will
  randomly fail with "No Error". This appears to be a problem with MIT
  kerberos, so will need to see about linking to heimdal if possible?
- The entire architecture behind LDAP and AD needs to be modified to
  work with GSSAPI "correctly". Right now, just to get it working,
  layers and layers of hacks have been implemented. This worries me as
  it just isn't tested.

Ticket: #6655