Use reinterpret cast is [does|may]PointTo

Instead of a straight up cast. Avoids problems related to opCast or alias this, such as those in:
http://forum.dlang.org/thread/vldwvnuivsfwjozqiuup@forum.dlang.org
Why not I guess. Which module though? Functional? I'll do a quick grep to see where it's used: I hate introducing new things for single use, when it could be used in other places too.