First attempt at getting block-sort to work. This is an incremental check-in.

There are many problems still to be worked out.

FossilOrigin-Name: 59742dd4c5259883850044d0938248b009ebd045

src/vdbeInt.h

@@ -72,6 +72,7 @@ struct VdbeCursor {
   u8 nullRow;           /* True if pointing to a row with no data */
   u8 rowidIsValid;      /* True if lastRowid is valid */
   u8 deferredMoveto;    /* A call to sqlite3BtreeMoveto() is needed */
+  Bool isEphemeral:1;   /* True for an ephemeral table */
   Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
   Bool isTable:1;       /* True if a table requiring integer keys */
   Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */