CLooG: Do not take into account the context

CLooG and the CLooG based code generation does not yet correctly derive the
types of the expressions, but just uses i64 for everything. This is incorrect,
but works normally pretty well. However, the recent change of adding parameter
bounds to the context made CLooG generate expressions that contain a lot of very
large integers that possibly don't fit into an i64. This broke the code
generation for several benchmarks.

To get the CLooG based code generation working again, we just don't take into
account any constraints in the context. This brings us back to the theoretical
incorrect, but in practice generally correct code.

The next step will be the isl based code generation. Here we will derive
automatically correct types.

llvm-svn: 158015