Merge the latest trunk enhancements and fixes into the sessions branch.

FossilOrigin-Name: 4e5f17d189eb0578a544c21fc150f9e2ee3428e3

src/insert.c

@@ -2037,7 +2037,6 @@ static int xferOptimization(
       ** might change the definition of a collation sequence and then run
       ** a VACUUM command. In that case keys may not be written in strictly
       ** sorted order.  */
-      int i;
       for(i=0; i<pSrcIdx->nColumn; i++){
         char *zColl = pSrcIdx->azColl[i];
         assert( zColl!=0 );