popn: new cab windowed mode (#621)

## Link to GitHub Issue or related Pull Request, if one exists
#618 

## Description of change
Get windowed mode to work.

## Testing
tbd... i/o doesn't work right now but it launches two windows at
least...

src/spice2x/touch/touch.cpp

@@ -243,6 +243,7 @@ static LRESULT CALLBACK SpiceTouchWndProc(HWND hWnd, UINT msg, WPARAM wParam, LP
     const auto is_windowed_sub =
         (GRAPHICS_IIDX_WSUB && hWnd == TDJ_SUBSCREEN_WINDOW) ||
          (hWnd == SDVX_SUBSCREEN_WINDOW) ||
+         (hWnd == POPN_SUBSCREEN_WINDOW) ||
          (hWnd == GFDM_SUBSCREEN_WINDOW);
 
     if (msg == WM_CLOSE) {