Graphical switching between S-functions

Use a single Simulink s-function block to access multiple s-functions.

Allow users to switch between multiple s-functions from popup menu. The s-functions used in this example block ship with Simulink.
For more details, edit block mask and examine the parameters tab. The callback section will show the command that makes it possible -- "set_param(gcb,'functionname',get_param(gcb,'sfun'))".