dtfile: fix pointer to integer conversion

Use XtArgVal (usually (long)) to convert
(XtPointer) to (int) and back.

This provides safe way to convert and
avoids compiler warning.

cde/programs/dtfile/Main.c

@@ -5146,7 +5146,7 @@ CleanUp (
    XRectangle textExtent;
    Position x, y;
 
-   if ((int) client_data == FM_POPUP)
+   if ((int)(XtArgVal) client_data == FM_POPUP)
      mbar = XtParent(w);
    else
      mbar = XmGetPostedFromWidget(XtParent(w));