Do not verify the base addresses

Verification of base addresses is difficult as the independent blocks pass may
introduce aliasing that was not there during scop detection. As a midterm
solution -polly-codegen-scev will remove the need for the independent blocks
pass. For now, we do not verify at compile time that the independent blocks pass
does not make the base addresses loop invariant. Disabling this just removes
one of the multiple safety layers we have. We still can check for correctness
in our regression tests.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@200315 91177308-0d34-0410-b5e6-96231b3b80d8