define gcd 0 0 = 0 (Ticket #3304)

[roconnor at theorem.ca]

As much as I'd love gcd 0 0 to be 0, the major problem is that this change 
would contradict the Haskell 98 report.

Persumably the Haskell report needs to be changed first.

Is there a ticket for this for Haskell prime?  I didn't find one.

-- 
Russell O'Connor                                      <http://r6.ca/>
``All talk about `theft,''' the general counsel of the American Graphophone
Company wrote, ``is the merest claptrap, for there exists no property in
ideas musical, literary or artistic, except as defined by statute.''