[PATCH Committed]: scratch_buffer: Suppress truncation warning on 32-bit

[Paul Eggert]

Florian Weimer wrote:
>   	      && unchanged_array_size (&buf, 1ULL << 16, 0)
>   	      && unchanged_array_size (&buf, 0, 1ULL << 16)
> -	      && unchanged_array_size (&buf, 1ULL << 32, 0)
> -	      && unchanged_array_size (&buf, 0, 1ULL << 32)))
> +	      && unchanged_array_size (&buf, (size_t) (1ULL << 32), 0)
> +	      && unchanged_array_size (&buf, 0, (size_t) (1ULL << 32))))

A small point: it's better to avoid suffixes like "ULL" when it's easy, which is 
the case here.  The above can be written as:

               && unchanged_array_size (&buf, 1 << 16, 0)
               && unchanged_array_size (&buf, 0, 1 << 16)
               && unchanged_array_size (&buf, (size_t) 1 << 31 << 1, 0)
               && unchanged_array_size (&buf, 0, (size_t) 1 << 31 << 1)))