gcc specific attributes are used in the benchmarks

[kjetilos]

The benchmark code is using gcc specific attributes to mark unused parameters and function to not inline. Using gcc specific attributes will make the benchmark harder to port to non-gcc based compilers. This was seen when building the benchmarks with the IAR compiler. The IAR compiler has a way to enable gcc extensions, however it would be nice if the benchmark could build on any standard c compiler.

[jeremybennett]

Hi Kjetil,

Thanks for this, we'll sweep this up when we fix issue #72.