More aggressive use of EP_Leaf on expression nodes, to help prune searches.

FossilOrigin-Name: c1a1d68c8219c8072e60af5c46a30849ae9a04fa1a6b2a8b22b82fec069d691d
diff --git a/src/resolve.c b/src/resolve.c
index 8cddfd8..b13786f 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -478,6 +478,7 @@
   sqlite3ExprDelete(db, pExpr->pRight);
   pExpr->pRight = 0;
   pExpr->op = (isTrigger ? TK_TRIGGER : TK_COLUMN);
+  ExprSetProperty(pExpr, EP_Leaf);
 lookupname_end:
   if( cnt==1 ){
     assert( pNC!=0 );