Drastic impromvents to pam_winbind.

Drastic impromvents to pam_winbind.

This adds code to do generic PAM -> NTSTATUS and NTSTATUS -> PAM error
conversions, and uses them to make the error handling in pam_winbind sane.

In particular, pam_winbind now uses PAM error codes, not silly '-1, -2 ...'
stuff, and logs the NTSTATUS error that winbind now sends over the pipe.

Added code to wbinfo to display these - makes a big difference in debugging
winbindd.

The main change here is the code to allow pam_winbind password changing to
correctly stack - This code ripped from pam_unix, and the copyright attached.
(Same as for all pam modules, including pam_winbind)

Andrew Bartlett
(This used to be commit dc1a72f896b83bc1ad3c7bf6c12c36ace3967280)