truss: Add AIO syscalls.

Display the arguments of aio_read(2), aio_write(2), aio_suspend(2),
aio_error(2), aio_return(2), aio_cancel(2), aio_fsync(2), aio_mlock(2),
aio_waitcomplete(2) and lio_listio(2) in human-readable form.

Reviewed by: asomers
Differential Revision: https://reviews.freebsd.org/D27518