fix Octave benchmarks, broken by 7ed4a1152d.
Revert "vectorized computation of Mandelbroit"

This reverts commit 9eb773cc2752a4d3842ff137ae285c2d4f08ec8c.

This change should never have been merged in the first place. It
does the opposite of what we say the purpose of our benchmarks for.
If use vectorized Matlab code here, then we need to use it for all
of the other language that are lousy at iteration.
Merge branch 'master' of github.com:JuliaLang/julia