Revert "Added support for modulo expressions"

This reverts commit 215684. The intention of the commit is great, but
unfortunately it seems to be the cause of 14 LNT test suite failures:

http://lab.llvm.org:8011/builders/perf-x86_64-penryn-O3-polly/builds/116

To make our buildbots and performance testers green until this issue is solved,
we temporarily revert this commit.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@215816 91177308-0d34-0410-b5e6-96231b3b80d8