cleanup: const in List::push_front()

sql/sql_list.h

@@ -212,9 +212,9 @@ class base_list :public Sql_alloc
     }
     return 1;
   }
-  inline bool push_front(void *info)
+  inline bool push_front(const void *info)
   { return push_front_impl(new list_node(info, first)); }
-  inline bool push_front(void *info, MEM_ROOT *mem_root)
+  inline bool push_front(const void *info, MEM_ROOT *mem_root)
   { return push_front_impl(new (mem_root) list_node(info,first)); }
   void remove(list_node **prev)
   {
@@ -503,8 +503,8 @@ template <class T> class List :public base_list
   inline bool push_back(T *a) { return base_list::push_back(a); }
   inline bool push_back(T *a, MEM_ROOT *mem_root)
   { return base_list::push_back((void*) a, mem_root); }
-  inline bool push_front(T *a) { return base_list::push_front(a); }
-  inline bool push_front(T *a, MEM_ROOT *mem_root)
+  inline bool push_front(const T *a) { return base_list::push_front(a); }
+  inline bool push_front(const T *a, MEM_ROOT *mem_root)
   { return base_list::push_front((void*) a, mem_root); }
   inline T* head() {return (T*) base_list::head(); }
   inline T** head_ref() {return (T**) base_list::head_ref(); }