[polly] record delinearization result and reuse it in polyhedral translation

[Tobias Grosser]

On 01/06/2014 18:14, Sebastian Pop wrote:
> Hi,
>
> this is the last piece of the rewrite of the delinearization split in 3 steps:
> it removes the last call to SCEV->delinearize in polly and replaces it with
> reading the cached previously computed delinearization.
>
> Ok to commit?

This looks good in general, but it would be good to explain _why_ we are 
doing this and to provide a test case that shows that this is necessary.

Tobias