* server.el (server-sentinel): Uncomment code to delete connection file.
(server-start): Save the connection file in the server property list.
Delete it only when we are reasonably convinced that it is not owned by
a running server.
(server-force-delete): New command to force-delete the connection file,
and stop the server if it is running.
(server-running-p): Return t also for local TCP servers when we find a
process with a matching PID, and :other for undecided cases.