anchor.diff:          Assert.AreEqual((123I + 456I),579I)
           Assert.AreEqual((-123I + (-456I)),-579I)
           Assert.AreEqual((0I + 123I),123I)
  -#if MONO // see https://bugzilla.xamarin.com/show_bug.cgi?id=22591
  +#if CROSS_PLATFORM_COMPILER // see https://bugzilla.xamarin.com/show_bug.cgi?id=22591
   #else
           Assert.AreEqual((BigInteger() + 123I),123I)
           Assert.AreEqual((123I + BigInteger()),123I)
  
positive.code:         Assert.IsFalse(-0I.IsOne)
          Assert.IsFalse(BigInteger.Zero.IsOne)
          Assert.IsFalse((-BigInteger.Zero).IsOne)
  #if MONO // see https://bugzilla.xamarin.com/show_bug.cgi?id=22591
  #else
          Assert.IsFalse(BigInteger().IsOne)
          Assert.IsFalse((-BigInteger()).IsOne)
  
negative.code:         q <- BigInteger.DivRem(0I, 100I, &r)
          Assert.AreEqual((q,r), (0I, 0I))
  
  #if CROSS_PLATFORM_COMPILER // see https://bugzilla.xamarin.com/show_bug.cgi?id=22591
  #else
          qr <- BigInteger.DivRem(BigInteger(), 1I)
          Assert.AreEqual(qr, (0I, 0I))
  