Benchmark tweaks:

* Added pi_sum_vec to Matlab, Julia and R (disabled)
* Tweaked parseint in perf.R
* Added perf.lua by Francesco Abatte (Needs the GSL Shell)
perf: Lua corrections and pi_sum_vec in Python (disabled)
perf.lua: fix oversight
perf.R: cache the pi_sum_vec range to match other implementations.
perf.lua: Adding pure Lua variants.
perf.lua: Removed pure Lua variants

... since the GSL and Julia use the same PRNG, and LuaJIT does not.
Merge pull request #2278 from pygy/PerfTests

RFC: Benchmark tweaks