Make the ORDER BY clause return equal elements in the same order they were

seen (a stable sort).  It was returning them in exactly the reverse order. (CVS 2439)

FossilOrigin-Name: e8391491a68018406e30c2a699a4cab9e0de092c

src/vdbeaux.c

@@ -779,6 +779,7 @@ void sqlite3VdbeSorterReset(Vdbe *p){
     sqlite3VdbeMemRelease(&pSorter->data);
     sqliteFree(pSorter);
   }
+  p->pSortTail = 0;
 }
 
 /*