Better integrate the changes on this branch with OP_Insert and OP_IdxInsert.

FossilOrigin-Name: 101cef14910d6e865a94bc870aed599321b893188062a9a61d70a9434992cf23

src/btreeInt.h

@@ -455,6 +455,7 @@ struct BtShared {
   Btree *pWriter;       /* Btree with currently open write transaction */
 #endif
   u8 *pTmpSpace;        /* Temp space sufficient to hold a single cell */
+  int nPreformatSize;   /* Size of last cell written by TransferRow() */
 };
 
 /*