BUILD: haload: Increase a buffer size so that gcc will stop complaining

BUILD: haload: Increase a buffer size so that gcc will stop complaining

gcc 16 whines that in human_number(), the calls to snprintf() could lead
to a truncated output because the buffer is not big enough. This is not
really true, because we always have a limited number of digits, but gcc
can't figure that out, so just bump the buffer size from 5 bytes to 8
bytes to make gcc happy.