Extended stats

[Just Marc]

Hi,

Along with a few really nice extra stats proposed here recently (which 
really should be implemented by someone with some time on their hands), 
I'd like to see a stat that accounts the avg time per request for all 
requests in the past 5 mins / past 1h, etc.     I could be pretty 
beneficial in some uses, especially for people who push memcache to its 
limits and or are trying to isolate performance issues or like to 
monitor every aspects of their systems.

Thanks