Required by Super Arcade Racing.
GetPointerInfo() can only succeed if WM_POINTER message are received, which can happen if there is a pointer device or EnableMouseInPointer(TRUE) is called. We don't currently send any WM_POINTER messages (and EnableMouseInPointer is a stub), so I hope adding a always failing stub won't break anything.
-- v2: user32: Add stub for GetPointerInfo().