Alternate fix to delete queries with aliases.

I goofed on the last set of changes and mainlined a MySQLism. Since we don't support joins in delete queries, and database vendors either don't support aliases in delete queries (sqlite) or support them in different ways (mysql, postgres, sqlserver) it is simpler to manipulate queries before they are rendered removing table and condition aliases.
better use `traverse()` it will get go to the deepest level.