adds a new variable `gnus-sum-thread-tree-adopted-leaf' which is used
for adopted leaves (leaves that would have `<' as opening bracket).

 Question 1: Is it, under any circumstances possible that an adopted
 article has brothers? (I.e. do I need
 `gnus-sum-thread-tree-adopted-leaf-with-other'?

 Question 2: Could this be integrated into Oort?

 Question 3: The patch is optimized for size ;-) Should the line

          (if (eq gnus-tmp-opening-bracket ?\<) 

 be changed so that it doesn't depend on gnus-tmp-opening bracket? 
 Maybe the information `<' or `[' should be factored out into some
 variable. What would be its name?


	Martin

 PS: In Emacs 21, ASCII art does not nearly look as good as unicode art
so I chose these settings under X with the quite complete fixed font:

(setq gnus-sum-thread-tree-root "■ ")
(setq gnus-sum-thread-tree-single-indent "□ ")
(setq gnus-sum-thread-tree-vertical "│ ")
(setq gnus-sum-thread-tree-indent "  ")
(setq gnus-sum-thread-tree-leaf-with-other "├─▶ ")
(setq gnus-sum-thread-tree-single-leaf "╰─▶ ")
(setq gnus-sum-thread-tree-adopted-leaf "╰╶▷ ")

Producing this Summary

O   14-Aug Jason R. Mastaler       (  21) ■ Re: gnus-delay.el: let Gnus remind you of action items 
O   15-Aug Kai Großjohann          (  26)   ├─▶  
O   15-Aug Jason R. Mastaler       (  14)   │ ╰─▶  
O   15-Aug Kai Großjohann          (  14)   ╰─▶  
O   19-Aug Lars Magne Ingebrigtse  (  15)     ╰╶▷  
O   20-Aug Kai Großjohann          (  30)       ╰─▶  
O   20-Aug Lars Magne Ingebrigtse  (  17)         ├─▶  
O   20-Aug Kai Großjohann          (  19)         ╰─▶