Fix non-threaded $sort_aux "reverse-" sorting.

Fix non-threaded $sort_aux "reverse-" sorting.

The secondary sort was looking at (Sort & SORT_REVERSE) instead
of (SortAux & SORT_REVERSE), so wasn't even performing the reverse
based on the correct flag.

Additionally, afterwards, the primary sort was improperly applying a
reverse when the secondary sort returned non-zero.

Change SORTCODE() to look at SortAux when we are inside a secondary
sort.

Change AUXSORT() to return the result if the secondary sort returns
non-zero.  It is ugly to put a return inside the macro, but the check
for non-zero needs to be performed inside the AUXSORT if branch.

If the secondary sort returns 0, then the primary sort can still
compare index and apply a reverse as needed.