build-sys: fix bad cast on win64
build-sys: fix bad cast on win64

spice-widget.c:814:50: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
         g_return_if_fail(SystemParametersInfo(SPI_SETMOUSESPEED, 0, (PVOID)d->win_mouse_speed, 0));

Fantu/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,elmarco/spice-gtk,elmarco/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,guodong/spice-gtk,flexVDI/spice-gtk,Fantu/spice-gtk,Fantu/spice-gtk,elmarco/spice-gtk,guodong/spice-gtk,Fantu/spice-gtk,fgouget/spice-gtk,SPICE/spice-gtk,guodong/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,SPICE/spice-gtk,fgouget/spice-gtk,elmarco/spice-gtk