Cannot add joins to taxonomy migration classes because vid becomes ambiguous

The Drupal 5 and Drupal 6 term migration classes contain this condition in their query:

$query->condition('vid', explode(',', $this->sourceVocabulary), 'IN')

This causes the 'vid' becoming ambiguous when adding joins to tables with a 'vid' column. For example when adding a join on term_node because i only want to migrate terms used in published nodes or used in certain node type.

It can be fixed by simply adding 'td.vid' as condition instead of 'vid'.

Patch coming when i have a node id.