Missing headers from SharedMem.hsc

[Simon Marlow]

Don Stewart wrote:
> It was also missing HsUnix.h, so the #defines weren't propagating
> anyway.
> 
> 
> Mon Jan 12 15:07:58 PST 2009  Don Stewart <dons at galois.com>
>   * Add check for -lrt to get the shm* functions. Subst. in buildinfo
> 
> Mon Jan 12 15:47:17 PST 2009  Don Stewart <dons at galois.com>
>   * SharedMem.hsc wasn't including HsUnixConfig.h, so no #defines were propagating

Pushed, eventually.

Cheers,
	Simon