IupSetFunction
Associates a function to a global callback name, such as IDLE_ACTION, ENTRY_POINT, and the GLOBAL*_CB family.
Parameters/Return
Icallback IupSetFunction(const char *name, Icallback func);name: name of the global callback.
func: address of a C function. If NULL removes the
association.
Returns: the address of the previous function associated to the name.