slow coercion of polynomial to list over integer mod ring

[dmharvey]

Sage 4.5.3, 2.6GHz Opteron, Linux

sage: R = Integers(3^20)
sage: S.<x> = PolynomialRing(R)
sage: f = S([R.random_element() for i in range(100)])
sage: timeit("L = f.list()")
125 loops, best of 3: 1.13 ms per loop

That's about 29000 cycles per coefficient conversion. See also #9883.

[roed]

This is sped up by about a factor of 33 by the patch at #9887. If that's positively reviewed, I would suggest closing this ticket.