[Ati2]

Feature request:

When a user already has a congratulating thread, do not make a new one for him.

Possible scenarios:

* user posts, reaches the milestone, then deletes his post, then posts again, deletes his post etc. new threads get created each time.
* user posts, then his next post comes in a forum where posts are not counted, so his postcount stays at, say 1000. new threads get created each time.

Less likely scenario:

* another mod interferes, and short posts are not counted, so his postcount remains at the milestone mark. this is basically the same as point 2 above.

Possible solution:

* create the thread name, and see if there is already a thread title like that (by the same author, as the script runs). if there is, do not create the thread.