div_qr_1 interface

[Torbjorn Granlund]

nisse at lysator.liu.se (Niels Möller) writes:

  Fixed now.
  
  > Then there's another problem with n==2, which needs a bit more
  > debugging.
  
  Problem was that the q limb is written a bit too early, breaking overlap
  operation. Maybe that ought to be fixed, but for now I changed try.c to
  not allow any overlap.
  
Basically qp = up won't work, but qp = up + k for any positive k will?
Does the C code share that property?

I think it would be good to fix that, since it is surely a common usage
scenario.  Furthermore, divrem_1 falling back to the new stuff would
need some complications if we disallow full overlap.

-- 
Torbjörn