load script after initial registry burst

This makes the logic of installing idle handlers and layout handlers a bit
cleaner and allows us to send wayland request from the script in the future.

src/call-exit-handler.h

@@ -1,6 +1,6 @@
 #ifndef RIVERGUILE_CALL_EXIT_HANDLER_H
 #define RIVERGUILE_CALL_EXIT_HANDLER_H
 
-void *call_exit_handler (void);
+void *call_exit_handler (void* data);
 
 #endif