[PATCH] Add math benchmark latency test

[Wilco Dijkstra]

Siddhesh Poyarekar wrote:
>
> BTW, this will only work for functions that have the same first argument
> and return types.  This is OK for now, but it might be something to fix
> in future.  A comment to that effect in the code would be very useful
> because I'm pretty sure I'll forget about it in the next 15 minutes or
> so and Wilco will too, maybe later than that :)

I've added a comment. It would fail on say pointer + float but works fine
if the types support addition between them. The latency test doesn't work
for sincos (somehow the madd is left out), but I'll fix that when I add a
workload for it.

Wilco