createNextIterationMap from C to C++ interface

Summary: update createNextIterationMap function to new C++ interface.

Reviewers: grosser, Meinersbur, jdoerfert, bollu, cs15btech11044

Reviewed By: cs15btech11044

Subscribers: llvm-commits, pollydev

Tags: #polly

Differential Revision: https://reviews.llvm.org/D47102

llvm-svn: 333113