various: Window objects should be initialised to 0 not NULL

cde/programs/dtksh/dtkcmds.c

@@ -2476,7 +2476,7 @@ invokeXDrawFunction(
    char * functionName = argv[0];
    Display * display;
    Window drawable;
-   Window destination = NULL;
+   Window destination = 0;
    int srcX = 0, srcY = 0;
    int destX = 0, destY = 0;
    unsigned int width = 0, height = 0;

cde/programs/dtlogin/session.c

@@ -365,7 +365,7 @@ void
 ManageSession( struct display *d )
 {
     int			pid;
-    Window		root = NULL;
+    Window		root = 0;
    /* Display 		*dpy; */
 #ifdef BYPASSLOGIN
     char	*BypassUsername;

cde/programs/dtprintinfo/libUI/MotifUI/MainWindow.C

@@ -222,7 +222,7 @@ void MainWindow::PopupMenu(Widget widget, XtPointer client_data,
 {
    XRectangle          pixmap_rect, label_rect;
    XButtonEvent *      ev;
-   Window              child, parent = NULL, root;
+   Window              child, parent = 0, root;
    int                 root_x, root_y, win_x, win_y;
    unsigned int        modMask;
    Display *           display = XtDisplay(widget);