Try to avoid field extensions during factorization.
Spent less time in rational reconstruction.
Use heuristic gcd also for high degree.
do not evaluate coefficients too eagerly.
delete unused line.
Faster coercions for univariate polynomials.
Cache function lookups during coercions.
Faster polynomial multiplication in commutative case.
Faster 'univariate'.
Faster 'map' for univariate polynomials.