Print ring occupancy statistics on shutdown

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Display segments per request stats on shutdown

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Display total request/response counters on shutdown.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #15 from djs55/stats

Display ring stats on shutdown