implement same benchmarks as redis-benchmark in C

with comparable results and rnd variant for comparison

(I do see some fuzz in results of perl benchmark
which aren't there for C version, so I suspect perl
as culprit, and not Redis :-)

git-svn-id: svn+ssh://llin/home/dpavlin/private/svn/Redis@56 447b33ff-793d-4489-8442-9bea7d161be5