Fixes deformation of dialog upon movement under Win10

[RamonUnch]

See: https://github.com/RamonUnch/AltDrag/issues/76 This mostly concerns the file explorer dialog boxes. You just need to use the SWP_ASYNCWINDOWPOS flag when moving the window.

EDIT: I would say not to merge it because it can induce more problems with some other programs. I ended up using a separated thread for window movement, using SWP_ASYNCWINDOWPOS flag only in some specific cases.