Fix typo in alignment check

It checks percentile_list twice and forgets latency_percentile
in the thread_options_pack structure. Add alignment after the
32-bit sync_file_range to make it align properly.

Signed-off-by: Jens Axboe <axboe@fb.com>
compiler: improve gcc 4.x compile time check

Signed-off-by: Jens Axboe <axboe@fb.com>