make method const

Closes #677

sql/handler.cc

@@ -7465,7 +7465,8 @@ static bool require_bigint(const Create_field *f, Lex_table_name table_name)
 
 bool Vers_parse_info::check_sys_fields(const Lex_table_name &table_name,
                                        const Lex_table_name &db,
-                                       Alter_info *alter_info, bool can_native)
+                                       Alter_info *alter_info,
+                                       bool can_native) const
 {
   if (check_conditions(table_name, db))
     return true;

sql/handler.h

@@ -1989,8 +1989,8 @@ struct Vers_parse_info
   bool fix_create_like(Alter_info &alter_info, HA_CREATE_INFO &create_info,
                        TABLE_LIST &src_table, TABLE_LIST &table);
   bool check_sys_fields(const Lex_table_name &table_name,
-                        const Lex_table_name &db,
-                        Alter_info *alter_info, bool can_native);
+                        const Lex_table_name &db, Alter_info *alter_info,
+                        bool can_native) const;
 
   /**
      At least one field was specified 'WITH/WITHOUT SYSTEM VERSIONING'.