Provide hints to the btree layer during the creation of transient tables

when it is possible for those tables to use a hash rather than a binary tree.
No use is current made of those hints, though assert() statement verify
their accuracy.

FossilOrigin-Name: 4fead8e714c7e50a9d246467e62bc846ef6180a0

src/update.c

@@ -638,6 +638,7 @@ static void updateVirtualTable(
   assert( v );
   ephemTab = pParse->nTab++;
   sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));
+  sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
 
   /* fill the ephemeral table 
   */