add listbox widget.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@696 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/rtgui/SConscript

@@ -45,6 +45,7 @@ widgets/radiobox.c
 widgets/slider.c
 widgets/staticline.c
 widgets/textbox.c
+widgets/listbox.c
 widgets/title.c
 widgets/toplevel.c
 widgets/view.c