vollt

[ADQL] Fix a Big Bug reported by M.Taylor and M.Demleitner: in ORDER BY, GROUP BY and USING only regular and delimited identifiers are accepted, not qualified column names.
For instance: "SELECT table.column_name FROM table ORDER BY table.column_name" is wrong. We should instead write:
"SELECT table.column_name FROM table ORDER BY column_name".
"SELECT table.column_name AS mycol FROM table ORDER BY mycol" is also correct.
Of course, for ORDER BY and GROUP BY, it is still possible to reference a column using its index in the SELECT clause.
For instance: "SELECT table.column_name FROM table ORDER BY 1".