Bug#16359402 CRASH WITH AGGREGATES: ASSERTION FAILED: N < M_SIZE

Post push fix:
setup_ref_array() now uses n_sum_items to determine size of ref_pointer_array.
The problem was that n_sum_items kept growing, it wasn't reset for each query.

A similar memory leak was fixed with the patch for:
Bug 14683676 ENDLESS MEMORY CONSUMPTION IN SETUP_REF_ARRAY WITH MAX IN SUBQUERY


sql/sql_yacc.yy:
  Reset parsing_place when we're done parsing SHOW commands, 
  to prevent Item::Item incrementing select_n_having_items
  (which is also used in setup_ref_array())

sql/sql_lex.cc

@@ -1761,6 +1761,7 @@ void st_select_lex::init_query()
   ref_pointer_array_size= 0;
   select_n_where_fields= 0;
   select_n_having_items= 0;
+  n_sum_items= 0;
   n_child_sum_items= 0;
   subquery_in_having= explicit_limit= 0;
   is_item_list_lookup= 0;

sql/sql_yacc.yy

@@ -10959,7 +10959,9 @@ show:
             bzero((char*) &lex->create_info,sizeof(lex->create_info));
           }
           show_param
-          {}
+          {
+            Select->parsing_place= NO_MATTER;
+          }
         ;
 
 show_param:
@@ -11309,7 +11311,10 @@ describe:
             if (prepare_schema_table(YYTHD, lex, $2, SCH_COLUMNS))
               MYSQL_YYABORT;
           }
-          opt_describe_column {}
+          opt_describe_column
+          {
+            Select->parsing_place= NO_MATTER;
+          }
         | describe_command opt_extended_describe
           { Lex->describe|= DESCRIBE_NORMAL; }
           select