hits found in the non-current file into the current file.

For the 40-hour trace starting on Sept 4 at 6pm, this increases the
hit rate from 83.2% to 87.0% (IOW a decrease in miss rate from 16.8%
to 13%):

ZEOCacheSimulation, cache size 200,000,000 bytes
  START TIME  DURATION    LOADS     HITS INVALS WRITES  FLIPS HITRATE
Sep  4 18:00  40:36:34  1420070  1181176  16198  10014     15  83.2%

AltZEOCacheSimulation, cache size 200,000,000 bytes
  START TIME  DURATION    LOADS     HITS INVALS WRITES  FLIPS HITRATE
Sep  4 18:00  40:36:34  1420070  1235770  15384  10014     25  87.0%