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

FossilOrigin-Name: c1a1d68c8219c8072e60af5c46a30849ae9a04fa1a6b2a8b22b82fec069d691d
diff --git a/src/expr.c b/src/expr.c
index fc24ffb..2e8b196 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -744,7 +744,7 @@
     pNew->iAgg = -1;
     if( pToken ){
       if( nExtra==0 ){
-        pNew->flags |= EP_IntValue;
+        pNew->flags |= EP_IntValue|EP_Leaf;
         pNew->u.iValue = iValue;
       }else{
         pNew->u.zToken = (char*)&pNew[1];