Trivial clean-up patch for stl_tree

[Paolo Carlini]

Hi Gawain,

> Hello,
>
> Here's a trivial clean-up patch for stl_tree.  I noticed a few months 
> ago but, well, this is clearly not urgent for anyone...

trivial, indeed, but unfortunately doesn't pass make-check-abi, because 
the functions are exported...

> I was also thinking of contributing other patches for stl_tree.h to 
> factorize some of the code, unless there is any objection or perhaps 
> this is not the right time for such patches which may well change the 
> ABI?   - How's that for a run-on sentence ;-)

For 4.2.0 we are not breaking the ABI, therefore you should target 
v7-branch for that kind of changes. And I'm pretty sure there is a lot 
of room for clean-ups, it would be great if you could figure out an 
ABI-safe set of changes for the current ABI... (this project was in my 
TODO, but you are super-super-welcome!)

Thanks,
Paolo.