[circle] changes to /find

[Thomas Voegtlin]

I commited a few changes to the /find command:

1. search results are displayed atomically.
i.e. the list of results is displayed as a 
single block, even if some new fields are 
created in the meantime by other tasks. 

2. /find -f finds a file.
/get to download it.
it works in text mode too.

3. find_task uses a Search_tree_interior object