Benchmarking for 2.18
Patch: Minor tweak to mp multiplication
Description: A minor tweak to the multiplication function (__mul) to help the compiler a bit to generate slightly faster code. It adds a local variable zk that acts as an accumulator across the loops (and within them) to reduce the reads to/writes from the array z.d.
Benchmark: Benchmark suite. Environment: Intel(R) Core(TM) i7-3520M CPU, Fedora 17 x86_64.
Criteria for acceptance: This results in an improvement of about 5% on x86_64 for the pow function.