MDEV-19740: Fix C++11 violations caught by GCC 9.2.1

sql/item.h

@@ -2,7 +2,7 @@
 #define SQL_ITEM_INCLUDED
 
 /* Copyright (c) 2000, 2017, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2018, MariaDB Corporation
+   Copyright (c) 2009, 2019, MariaDB Corporation.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -651,7 +651,6 @@ class Item: public Value_source,
             public Type_std_attributes,
             public Type_handler
 {
-  void operator=(Item &);
   /**
     The index in the JOIN::join_tab array of the JOIN_TAB this Item is attached
     to. Items are attached (or 'pushed') to JOIN_TABs during optimization by the

sql/sql_list.h

 #ifndef INCLUDES_MYSQL_SQL_LIST_H
 #define INCLUDES_MYSQL_SQL_LIST_H
 /* Copyright (c) 2000, 2012, Oracle and/or its affiliates.
+   Copyright (c) 2019, MariaDB Corporation.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -86,6 +87,14 @@ class SQL_I_List :public Sql_alloc
     next= elements ? tmp.next : &first;
   }
 
+  SQL_I_List& operator=(const SQL_I_List &tmp)
+  {
+    elements= tmp.elements;
+    first= tmp.first;
+    next= tmp.next;
+    return *this;
+  }
+
   inline void empty()
   {
     elements= 0;
@@ -176,6 +185,13 @@ class base_list :public Sql_alloc
       first == rhs.first &&
       last == rhs.last;
   }
+  base_list& operator=(const base_list &rhs)
+  {
+    elements= rhs.elements;
+    first= rhs.first;
+    last= elements ? rhs.last : &first;
+    return *this;
+  }
 
   inline void empty() { elements=0; first= &end_of_list; last=&first;}
   inline base_list() { empty(); }
@@ -190,9 +206,7 @@ class base_list :public Sql_alloc
   */
   inline base_list(const base_list &tmp) :Sql_alloc()
   {
-    elements= tmp.elements;
-    first= tmp.first;
-    last= elements ? tmp.last : &first;
+    *this= tmp;
   }
   /**
     Construct a deep copy of the argument in memory root mem_root.
@@ -202,7 +216,7 @@ class base_list :public Sql_alloc
   */
   bool copy(const base_list *rhs, MEM_ROOT *mem_root);
   base_list(const base_list &rhs, MEM_ROOT *mem_root) { copy(&rhs, mem_root); }
-  inline base_list(bool error) { }
+  inline base_list(bool) {}
   inline bool push_back(void *info)
   {
     if (((*last)=new list_node(info, &end_of_list)))
@@ -523,7 +537,6 @@ template <class T> class List :public base_list
 {
 public:
   inline List() :base_list() {}
-  inline List(const List<T> &tmp) :base_list(tmp) {}
   inline List(const List<T> &tmp, MEM_ROOT *mem_root) :
     base_list(tmp, mem_root) {}
   inline bool push_back(T *a) { return base_list::push_back(a); }