Cofactor canonicalisation of mpn_gcdext

[Torbjorn Granlund]

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

  For the case u = v, you prefer s = 0, t = 1 rather than s = 1, t = 0?
  
At the mpn level, we might choose not to pin things down for degenerate
cases, unless it can be done for free.

Specifically, we don't want to start or end each mpn function with a set
of rules and conditional adjustments for such cases.  This is against
the mpn spirit.

We should do what most callers want unless it is for free, and leave the
rest to callers that care.

-- 
Torbjörn