Allow ROW_NUMBER as unquoted column name

Since 10.7.1 ROW_NUMBER has become a reserved keyword, used within the GET DIAGNOSTICS command only.

Sine then ROW_NUMBER can only be used as a column name when quoted (with backticks, or with double quotes in ORACLE mode), which can break older applications that worked with 10.6 and older.

As ROW_NUMBER is used as a keyword in GET DIAGNOSTICS only it should be possible to use it unquoted in contexts where a column name is referenced.

I added ROW_NUMBER_SYM to the keyword_data_type: list in sql/sql_yacc.cc and could build the server, and run make test and the full test suite in mariadb-test/ just fine.