[development] Schema API committed for D6

Dries committed the Schema API patch this morning. Henceforth, all tables should be declared in .schema files and update functions should use the Schema API instead of explicit SQL or the former pgsql-only db_add_column()/db_change_column() functions in update.php. (Explicit SQL and those pgsql-functions will keep working, of course, so this does not represent a "flag day" for contrib.) The schema.module in contrib will automatically generate a schema data structure for any table that already exists in the database; you can then copy and paste it into your .schema file. I'll be writing some handbook pages for all of this in the near future. Thanks, Barry