During btree index build, sort equal-keyed tuples according to their

During btree index build, sort equal-keyed tuples according to their
TID (heap position).  This doesn't do anything to the validity of the
finished index, but by pretending to qsort() that there are no really
equal keys in the sort, we can avoid performance problems with qsort
implementations that have trouble with large numbers of equal keys.
Patch from Manfred Koizar.