Fix gfio build due to disk_stat struct seperation

Signed-off-by: Daniel Gollub <d.gollub@telekom.de>
Cc: Daniel Gollub <daniel.gollub@t-online.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Rename time.h for third-party include of fio.h

External project might build external ioengines and need to
include there for fio.h. If a project set the include path
to the fio root source directory and the third-party source
holds an "time.h" as well things get complicated.

Signed-off-by: Daniel Gollub <d.gollub@telekom.de>
Cc: Daniel Gollub <daniel.gollub@t-online.de>
Signed-off-by: Jens Axboe <axboe@fb.com>