openssh.inc: cleanup

openssh.inc: cleanup

Because of leading slashes in FILES_*, some files were being installed
twice: e.g. /etc/ssh/moduli was in both openssh and openssh-sshd. Now
openssh is an empty metapackage, which I think was the plan.

Other cleanups:
* switch to INC_PR
* remove dangling slogin symlink to ssh to fix warning
* remove FILES_openssh-dbg line, which had a syntax error and doesn't
  appear necessary to keep debug out of the openssh-misc package anymore.
* rename package ssh-keygen to openssh-keygen for consistency
* use ${PN} in variable names

Tested with 5.2p1.

Signed-off-by: Michael Smith <msmith@cbnco.com>