de-virtualize redundantly virtual Item method

and remove a couple of useless MY_TEST's

sql/item.h

@@ -2392,7 +2392,7 @@ class Item: public Value_source,
     if (join_tab_idx_arg < join_tab_idx)
       join_tab_idx= join_tab_idx_arg;
   }
-  virtual uint get_join_tab_idx() { return join_tab_idx; }
+  uint get_join_tab_idx() const { return join_tab_idx; }
 
   table_map view_used_tables(TABLE_LIST *view)
   {

sql/opt_index_cond_pushdown.cc

@@ -206,7 +206,7 @@ static Item *make_cond_for_index(THD *thd, Item *cond, TABLE *table, uint keyno,
 	  new_cond->argument_list()->push_back(fix, thd->mem_root);
           used_tables|= fix->used_tables();
         }
-        if (MY_TEST(item->marker == ICP_COND_USES_INDEX_ONLY))
+        if (item->marker == ICP_COND_USES_INDEX_ONLY)
         {
           n_marked++;
           item->marker= 0;
@@ -239,7 +239,7 @@ static Item *make_cond_for_index(THD *thd, Item *cond, TABLE *table, uint keyno,
 	if (!fix)
 	  return (COND*) 0;
 	new_cond->argument_list()->push_back(fix, thd->mem_root);
-        if (MY_TEST(item->marker == ICP_COND_USES_INDEX_ONLY))
+        if (item->marker == ICP_COND_USES_INDEX_ONLY)
         {
           n_marked++;
           item->marker= 0;