enable informing arithmetic parser of implicit units

This is so that "runtime=100" can be interpreted as 100 seconds
rather than 100 microseconds, but runtime=(100ms + 100s) can also
get the right answer (in microseconds).

Signed-off-by: Stephen M. Cameron <stephenmcameron@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
4 files changed