add rule for sum' Int
add rule for sum' Int

Ignore-this: 7f73d952716391ff235681a40a7b32c

darcs-hash:20100729225737-1a7c6-0285f7a9c8b1396c05708176271ea370f18b4b9a

kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc