Remove 'reduce for histograms' step

This choice has been made for performances purpose.
The reduce algorithm was proved less efficient than an atomicAdd version in one kernel, mainly due to non-concealed accesses to histograms memory.

Some experiments on 'reduce version' will maybe find a way to have a significant decrease in runtime using reduce kernel.
Add define statements for time measurements using CUDA
Merge branch 'cuda_fix_compile' into cuda_hog