First, update the return types of aio_return() and aio_waitcomplete() to
ssize_t.

POSIX requires aio_return() to return a ssize_t so that it can represent
all return values from read() and write().  aio_waitcomplete() should use
ssize_t for the same reason.

aio_return() has used ssize_t in <aio.h> since r31620 but the manpage and
system call entry were not updated.  aio_waitcomplete() has always
returned int.

Note that this does not require new system call stubs as this is
effectively only an API change in how the compiler interprets the return
value.

Second, allow aio_nbytes values up to IOSIZE_MAX instead of just INT_MAX.

aio_read/write should now honor the same length limits as normal read/write.

Third, use longs instead of ints in the aio_return() and aio_waitcomplete()
system call functions so that the 64-bit size_t in the in-kernel aiocb
isn't truncated to 32-bits before being copied out to userland or
being returned.

Finally, a simple test has been added to verify the bounds checking on the
maximum read size from a file.

PR:		191174
Submitted by:	Franco Fichtner  <franco at lastsummer.de>

Stop calling system calls "function calls".

Use "The .Fn system call" a-la "The .Nm utility".

When referring to a non-BSD implementation in
the HISTORY section, call syscall a function,
to be safe.

  linking.

* Fix disorder in the SEE ALSO sections of aio_*(2).

* Remove unnecessary cross-references from the SEE ALSO sections of
  aio_*(2); config(8), kldload(8) and kldunload(8) are cross-referenced
  from aio(4).

* Remove the KERNEL OPTIONS sections from aio_*(2), now that these
  pages cross-reference aio(4), which contains suitable kernel linking
  reference material.

Submitted by:	Craig Rodrigues <rodrigc@attbi.com>

Move Xref sections.

Submitted by: Craig Rodrigues <rodrigc@attbi.com>

Do not terminate the cross-reference list in the SEE ALSO section with
a period.