Delete unnecessary callback and dont use user32 for GetPtiCurrent

Hi @zeroSteiner,

Pull request with some 32 bits code cleanup, had to check harder, but this callback hadn't a lot of sense to me. I see you didn't include in the 64 bits version. Did some testing, and the 32 bits version is working smoothly also without it. So cleaning!

**EDIT**: I also have modified MyPtiCurrent to not rely on user32.dll. Works okey on my tests. Would be super if you could validate!