Allocate extra stack space for UnpackedRecord objects, reducing the need

to malloc for them as often, and thereby get a performance improvement.

FossilOrigin-Name: a725a75f870d7d9b21946fbcc71a956492986ab0

src/btree.c

@@ -684,7 +684,7 @@ static int btreeMoveto(
 ){
   int rc;                    /* Status code */
   UnpackedRecord *pIdxKey;   /* Unpacked index key */
-  char aSpace[150];          /* Temp space for pIdxKey - to avoid a malloc */
+  char aSpace[200];          /* Temp space for pIdxKey - to avoid a malloc */
   char *pFree = 0;
 
   if( pKey ){