update isl for export of isl_schedule to python interface
update isl for export of isl_schedule to python interface

This is needed for the python interface to pet, which contains
a method constructing an isl.schedule.

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

Meinersbur/ppcg,nicolasvasilache/ppcg,Meinersbur/ppcg,nicolasvasilache/ppcg