Fix two bugs affecting bonnie runs with large data files:
- A printf format specified a long operand but received an offset_t value.
- The random numbers for large seek ranges were computed without regard
for operator precedence and could become negative (for file sizes larger
than 4GB, which was a wrong test for "large", since it did not account
for the chunk size).
The problems were found by etc at fluffles dot net (Enlightenment). Thanks
for the detailed report. Guess there aren't many Bonnie users with multi-
terabyte RAID systems; these bugs had been found long ago, else ...