MDEV-4786 - merge 10.0-monty - 10.0

Fixed sys_vars.log_error_func, sys_vars.log_error_func2,
maria.small_blocksize, sys_vars.autocommit_func3, sys_vars.autocommit_func2,
sys_vars.autocommit_func4, sys_vars.autocommit_func5,
sys_vars.tx_isolation_func, main.pool_of_threads, innodb.innodb,
archive.archive-big, parts.part_supported_sql_func_innodb,
parts.partition_decimal_myisam, parts.partition_decimal_innodb,
main.sum_distinct-big, percona.innodb_sys_index,
percona.percona_flush_contiguous_neighbors failures.

libmysqld/lib_sql.cc:
  Restore proper method to retrieve warnings number.

libmysqld/lib_sql.cc

@@ -241,7 +241,7 @@ static my_bool emb_read_prepare_result(MYSQL *mysql, MYSQL_STMT *stmt)
   stmt->stmt_id= thd->client_stmt_id;
   stmt->param_count= thd->client_param_count;
   stmt->field_count= 0;
-  mysql->warning_count= thd->get_stmt_da()->statement_warn_count();
+  mysql->warning_count= thd->get_stmt_da()->current_statement_warn_count();
 
   if (thd->first_data)
   {
@@ -1045,7 +1045,7 @@ bool Protocol::send_result_set_metadata(List<Item> *list, uint flags)
 
   if (flags & SEND_EOF)
     write_eof_packet(thd, thd->server_status,
-                     thd->get_stmt_da()->statement_warn_count());
+                     thd->get_stmt_da()->current_statement_warn_count());
 
   DBUG_RETURN(prepare_for_send(list->elements));
  err: