On 64-bit machines, some values exported by /proc/diskstats, and then used by
iostat, can overflow.

For example:
Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s avgrq-sz
avgqu-sz   await  svctm  %util
sda          5.50   0.00 143.96  0.00 307496983987862656.00    0.00
153748491993931328.00     0.00 2136028725038430.00     7.94   55.12   5.59  80.42

The patch attached seems to fix those problems, but might cause problems with
the soft kABI. Patch is from Ben Woodward <woodward>