Allow to switch between Cuda and OpenCL if possible.
gpuUseCuda(bool)
%T : The toolbox use Cuda.
%F : The toolbox use OpenCL.
void : display what the toolbox use.
gpuUseCuda()
allows users to switch between Cuda and OpenCL
if the toolbox had been compiled with flag Cuda and OpenCL.
This function can be used without input parameter in order to displayed if the toolbox use Cuda or not.
If not, the toolbox use OpenCL.