[graphite] Backend fixes

[Sebastian Pop]

> Disable cloog optimizations
> ===========================
>
>  * graphite.c (set_cloog_options): Disable optimizations.
>
> Cloog optimizes the output in control flow.
>
> Example:
>
>          for (i = 0; i < 100; i ++)
>                if (i < 30 && i > 60)
>                        A
>          becomes:
>
>          for (i = 0; i < 30; i++)
>                A
>          for (i = 61; i < 100; i++)
>                A
>
> This breaks the current code generation, as some bbs may appear twice
> or more often in the clast output.
>

For fixing this one, we're replacing the bb_move with a bb_copy such
that we can handle also multiple copies of A.  This triggers also the
need of another cleanup for induction variables: we need exactly one
IV per loop, otherwise we end up with variable definitions that
disappears, as not renamed or moved along from the old loop.

Sebastian