r247953 - TypeSystem is now a plugin interface

Resending since the wrong list was CC’ed.

I was able to track this down to a bug in Clang. I have a patch up for review.

http://reviews.llvm.org/D13276

I’m not sure what part of the TypeSystem refactor caused this to finally be exposed, but in any case I expect that patch will go through and this bug will be fixed.