It looks like GCC 6 would benefit from an update of isl to 0.16.1 (but
NOT newer).  This would be an ABI bump of libisl to 15, so existing GCC
5 builds would not be affected, as long as we aren't planning any more
(and I sure hope we can move on at this point).  Achim, if JonY agrees,
would you be able to bump this?

-- 
Yaakov