extstore: automove script try #2.
extstore: automove script try #2.

using the new per-class free chunk limiter and ignoring item age, we can now
create a highly responsive page mover algorithm. It makes much fewer page
moves than before and keeps more of the free memory target in each class.

adjusts the per-class limits once per minute, and otherwise balancers by age.

memcached/memcached,gencer/memcached,memcached/memcached,gencer/memcached,dormando/memcached,dormando/memcached,gencer/memcached,dormando/memcached,dormando/memcached,memcached/memcached,dormando/memcached,gencer/memcached,memcached/memcached,memcached/memcached,gencer/memcached