gnu avl trees

[castironpi]

Hi,

I am copying the GNU Avl Tree library in another language (Python).  I
am adding 'up'-links, which I need for my application, and allowing
multiple equivalent keys.  So far, my implementation won't work for
long before entering a recursive loop on printing.

I'm continuing to diagnose and look for the bug, but I thought I'd
appeal to the older and wiser.  Anything to watch out for?  I'll post
the code if necessary, but it will take more explanation.