>
> How can I checkout that branch?
>

As I said earlier in this thread, you can have icomplete-vertical without 
using that branch, with the master branch you only need to `(setq 
icomplete-separator "\n")'.

If you want a more robust solution however (neither the above nor the 
branch are always correct), you'll have to wait.  If you don't want to 
wait, you can try my proposed solution (see attached), which works for any 
version of Emacs >= 24.