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
I know the intent is to test for successful compilation/linking. It's just that since we have the return values we might as well check them too.

But, this is really a nitpick. I'm OK with it if you decide to leave it the way it is now.