Fixup for 9975: swap and pointsTo

Fixing 9975 (http://d.puremagic.com/issues/show_bug.cgi?id=9975) revealed that checking `pointsTo` was creating problems in swap for legitimate use cases.

This is because:
1. pointsTo can sometimes create "false positives"
2. Internal pointing is not outright forbidden, it is just that the runtime is allowed to make the assumption they don't exist.

While swapping aliasing objects is a sign of stink, it should still "just work".