Port ScopInfo to the isl cpp bindings

Summary:
Most changes are mechanical, but in one place I changed the program semantics
by fixing a likely bug:

In `Scop::hasFeasibleRuntimeContext()`, I'm now explicitely handling the
error-case. Before, when the call to `addNonEmptyDomainConstraints()`
returned a null set, this (probably) accidentally worked because
isl_bool_error converts to true. I'm checking for nullptr now.

Reviewers: grosser, Meinersbur, bollu

Reviewed By: Meinersbur

Subscribers: nemanjai, kbarton, pollydev, llvm-commits

Differential Revision: https://reviews.llvm.org/D39971

llvm-svn: 318632
diff --git a/polly/lib/Transform/ForwardOpTree.cpp b/polly/lib/Transform/ForwardOpTree.cpp
index d31940d..dbdf8fc 100644
--- a/polly/lib/Transform/ForwardOpTree.cpp
+++ b/polly/lib/Transform/ForwardOpTree.cpp
@@ -962,7 +962,7 @@
     LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
 
     {
-      IslMaxOperationsGuard MaxOpGuard(S.getIslCtx(), MaxOps, false);
+      IslMaxOperationsGuard MaxOpGuard(S.getIslCtx().get(), MaxOps, false);
       Impl = llvm::make_unique<ForwardOpTreeImpl>(&S, &LI, MaxOpGuard);
 
       if (AnalyzeKnown) {