Sets the current sort column to be sort_column_id.
The this will resort itself to reflect this change, after emitting a `GtkTreeSortable:
GtkTreeSortable:sort-column-changed` signal. sort_column_id may either be a regular column id, or one of the
following special values:
| this |
A `GtkTreeSortable` |
| sort_column_id |
the sort column id to set |
| order |
The sort order of the column |