I've been working on support for OpenMP imperfectly-nested loops.  In 
the process I have gone astray multiple times because of 
incorrect/inadequate internal documentation for the OMP_FOR tree 
structure.  The code changes I've been working on are Stage 1 material, 
but the documentation improvements are independent and can be fixed now. 
  Here is a patch I put together for the internals manual; can other 
people familiar with this functionality review it for technical 
correctness?  Even after working with this code for months, I'm still 
not sure I understand all the nuances.  :-P  The comments in tree.def 
are also wrong, but once we get the content right in the manual I can 
just copy the changes there for the final version of the patch.

-Sandra