optimize znpoly arithmetic -- it's way, way too slow because of the polynomial template thingy

[was]

speeds up multiplication by a factor of *20* for many benchmarks... but causes a segfault when doctesting rings/arith.py

[jpflori]

Maybe this can be closed now... I'll run basic test laters.

[jpflori]

Based on the same idea (_mul_no_template_):

sage: K = Integers(2**6)
sage: R.<x> = K[]
sage: f = R([1,2,5,-9]); g = R([1,2,3,4])
sage: %timeit f._mul_zn_poly(g)
100000 loops, best of 3: 5.32 us per loop
sage: %timeit f._mul_(g)
1000000 loops, best of 3: 1 us per loop
sage: %timeit f._mul_no_template(g)
1000000 loops, best of 3: 790 ns per loop
sage: %timeit f*g
1000000 loops, best of 3: 845 ns per loop

So it seems the templating overhead is not so terrible. It also varies a little bit depending on the finite field. And it does not seem the templating code can be really trimmed down and further optimized.

So I suggest to close this ticket as won't fix.