5 argument gcd op

[Jens Rieks]

Hi,

I have written a gcd op that takes 5 arguments (3 out, 2 in)
        gcd d, x, y, a, b
and returns the gcd (in d) of a and b, as well as x and y so that
     d = gcd(a,b) = x*a + y*b

This op can be useful for some cryptographic stuff, should I check it in?
I've also written a test for it, as well as for "gcd int,num,num";
is a floating point version of this op useful?

  gcd(12.3, 24.6) = gcd(12.1, 24.2) = 12
but
  gcd(123.0, 246.0) = 123 != gcd(121, 242.0) = 121

jens