autoconf: set version to 6.3.1 for interim builds

Signed-off-by: Jeff Layton <jlayton@samba.org>
autoconf: allow PAM security install directory to be configurable

Allow the pam module install directory to be set at build time.

Signed-off-by: Jeff Layton <jlayton@samba.org>
cifs: use krb5_kt_default() to determine default keytab location

...don't assume that it's in /etc/krb5.keytab.

Reported-by: Konstantin Lepikhov <klepikho@redhat.com>
Signed-off-by: Jeff Layton <jlayton@samba.org>