BENCHTESTS: memmove benchtests do not test overlapping memory regions

[Anton Youdkevitch]

Folks,

The current testing framework is using two buffers
for all sorts of string benchmarks. Considering how
the buffers get allocated (using mmap with the first
argument set to 0) they can never overlap.

So, the memmove benchtest actually tests memcpy
(with a little additional startup) instead of memmove.
I would like to adapt memmove benchset to cover the
case of overlapping memory regions as well.

-- 
   Thanks,
   Anton