Now that we have .install files for modules, I believe it is time we
extended our database abstraction layer.

I recommend we create the following extra functions :

1. db_create_table($tablename, $columns); // columns is an
associative array with the 'name' => 'type'
3. db_drop_table($tablename);
3. db_create_index($tablename, $columns); // columns is an array of
column names, or just a single column.
4. db_drop_index($tablename, $columns);
5. db_add_column($tablename, $column, $type); // PGSQL already has a
similar function, but it isn't in both systems.
6. db_drop_column($tablename, $column);