adding a 'blocked' status for issues with a link to another issue

it'd be cool if you could set an issue to 'blocked', meaning that it's blocked on some other issue. that much we can do via the admin interface. however, it'd be even cooler if by setting it to blocked, you could input the nid of the issue it's blocked on (i'd have to think about how the UI should work for that) such that once that other issue was fixed/closed, the blocked one would automatically go back to being active. for example, at the time of this writing, http://drupal.org/node/64352 is currently blocked on http://drupal.org/node/59904. not that it's that hard to keep track of this particular case, but in general, i can imagine a lot of issues are in fact blocked on other things, and it'd be nice to track that stuff via status (and automatic status changes).