Add TD_F_SYNCS thread flag

Add TD_F_SYNCS thread flag

It's not enough to just track writes, some operating systems require
a file to be opened for write to issue a file sync. Which does kind
of make sense...

Add such a flag and set it for iolog/blktrace replay, if we see a sync
in there.

This does mean we need to bump the IO engine version, as the engine
flags need to get shifted.

Link: https://github.com/axboe/fio/issues/1352
Signed-off-by: Jens Axboe <axboe@kernel.dk>