#8/#39: Rework deny_remote / remove unknown_pts_as_local

[mcdope]

This reworks deny_remote handling to use process based checking.

Instead of checking utmp and hoping there is an entry for the current session, which there often isn't for virtual terminals, we now check the chain of parent processes. If any parent process is sshd or telnetd we deny authentication.

This renders unknown_pts_as_local obsolete - removed.

Closes #8 (again)
See #39

[mcdope]

Test build @ https://www.dropbox.com/s/rdwwiskezx7en2g/libpam-usb_0.7.3_amd64.deb?dl=0