Makefile changes to make compilation easier with MSVS + fix sleep

Concerning the changes, I have tested (well) with MSVS and it works. I guess when you say "At least it's not necessary on linux AFAIK", you are talking about the TODO in the Makefile concernning  or the #include <cstdint>. It doesn't compile/link without it with MSVS. Concerning cstdint, I didn't put it under MSVS flag because AFAIK, it exists with every configuration (but I may be wrong). Fill free to change if you think I'm wrong.