Fix Windows compile warnings, declarations of walk functions

sql/item_func.cc:
  Remove unused variable
sql/handler.cc:
  Fix warnings
sql/item_sum.cc:
  Restore C_MODE_START/END around count_distinct_walk
  Change second argument to dump_leaf_key to correct type
sql/item_sum.h:
  Change second argument to dump_leaf_key to correct type

sql/handler.cc

@@ -836,9 +836,9 @@ int ha_recover(HASH *commit_list)
   /* commit_list and tc_heuristic_recover cannot be set both */
   DBUG_ASSERT(commit_list==0 || tc_heuristic_recover==0);
   /* if either is set, total_ha_2pc must be set too */
-  DBUG_ASSERT(dry_run || total_ha_2pc>opt_bin_log);
+  DBUG_ASSERT(dry_run || total_ha_2pc>(ulong)opt_bin_log);
 
-  if (total_ha_2pc <= opt_bin_log)
+  if (total_ha_2pc <= (ulong)opt_bin_log)
     DBUG_RETURN(0);
 
   if (commit_list)

sql/item_func.cc

@@ -4683,7 +4683,6 @@ Field *
 Item_func_sp::tmp_table_field(TABLE *t_arg)
 {
   Field *res= 0;
-  enum_field_types ftype;
   DBUG_ENTER("Item_func_sp::tmp_table_field");
 
   if (m_sp)

sql/item_sum.cc

@@ -2158,12 +2158,16 @@ int composite_key_cmp(void* arg, byte* key1, byte* key2)
 }
 
 
+C_MODE_START
+
 static int count_distinct_walk(void *elem, element_count count, void *arg)
 {
   (*((ulonglong*)arg))++;
   return 0;
 }
 
+C_MODE_END
+
 
 void Item_sum_count_distinct::cleanup()
 {
@@ -2658,7 +2662,7 @@ int group_concat_key_cmp_with_distinct_and_order(void* arg,byte* key1,
   Append data from current leaf to item->result
 */
 
-int dump_leaf_key(byte* key, uint32 count __attribute__((unused)),
+int dump_leaf_key(byte* key, element_count count __attribute__((unused)),
                   Item_func_group_concat *item)
 {
   char buff[MAX_FIELD_WIDTH];

sql/item_sum.h

@@ -851,7 +851,8 @@ class Item_func_group_concat : public Item_sum
   friend int group_concat_key_cmp_with_distinct_and_order(void* arg,
 							byte* key1,
 							byte* key2);
-  friend int dump_leaf_key(byte* key, uint32 count __attribute__((unused)),
+  friend int dump_leaf_key(byte* key,
+                           element_count count __attribute__((unused)),
 			   Item_func_group_concat *group_concat_item);
 
  public: