headers/shlwapi: Change `QITAB.dwOffset` to `DWORD` for Windows 10 RS2+

It was an `int` up to Windows 10 RS1 (10.0.14393.0), but has been changed
to `DWORD` since RS2 (10.0.15063.0).

Reported-by: Cao GH <driver1998.ms@outlook.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>