fio: Fix (unsigned) integer overflow issues

fio: Fix (unsigned) integer overflow issues

This patch tries to address issues found when compiling fio with clang's
undefined behaviour sanitizer on 32 bit Linux. While this generated many
false positives it did identify a number of subtle issues when
rates/amounts/time calculations went above 32 bit values.

The following job was used:
[global]
time_based
runtime=180m
bs=256k
rw=randrw
norandommap
rate=512M
ioengine=null
direct=1
iodepth=8
thread
numjobs=10
ramp_time=20m

[null]
size=1P

It should fix https://github.com/axboe/fio/issues/270 because various 32
bit ETA variables were overflowing due to the microsecond arithmetic
being done on them (even on 64 bit systems).

This patch should also fix https://github.com/axboe/fio/issues/194 and
https://github.com/axboe/fio/issues/266 because 64 bit Windows is a
LLP64 platform so ints and longs still default to 32 bits.

Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>