x11/xforward: Permanently fix LLVM15 build error

Permanently fix:

xforward.c:528:87: error: incompatible pointer to integer conversion passing 'void *' to parameter of type 'Cardinal' (aka 'unsigned int') [-Wint-conversion]

topshell = XtAppCreateShell(NULL,"Xforward",applicationShellWidgetClass, dpy, NULL,NULL);
                                                                                   ^~~~