[Fix] isl usage errors in ScheduleOptimizer


git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@216084 91177308-0d34-0410-b5e6-96231b3b80d8
Update for LLVM api change

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@216394 91177308-0d34-0410-b5e6-96231b3b80d8