Fix AutoHandle (+tests)

[sergz]

I went through the code and have not found the wrong usage, but it should be prevented in the future.

• Sometimes the invalid value for the handle is INVALID_HANDLE_VALUE
• always returning the non zero pointer for operator PHANDLE() is not safe
• the behaviour of operator bool and operator HANDLE can be unexpected

Current interface

  operator HANDLE();
  operator PHANDLE();
  operator bool();

Which operator of handleX and handleY will be called in
resultCode = GetResource(someId, settings, handleX, handleY, timeout)?