Feature request: Allow custom directory for privilege separation in the configuration file. And change the pam module.

[Ramón García]

In order to be able to have different instances of sshd running in a
machine (for instance, one for system administrators, other for a file
transfer service) it should be useful:

- To allow the administrator to specify the name of the pam module, so
that one can create a customized file in /etc/pam.d
- A customized privilege separation directory.

At present I am using Linux mount --bind to have a different privilege
separation directory, but it is a kludge.

Best regards.