Adding options for tcp keep alive.

Adding more options for TCP Keep Alive like probe/intervals.  Example conf with the additional options:

<p><code>
# imtcp
module(
  load="imtcp"
  KeepAlive="on"
  KeepAlive.probes="3"
  Keepalive.Time="3"
  Keepalive.Interval="3"
)
</code></p>

The source might need to be cleaned up to meet rsyslog conventions.