Added code to make sure we don't recursively try to find an objective C

class. The thing with Objective C classes is the debug info might have a
definition that isn't just a forward decl, but it is incomplete. So we need to
look and see if we can find the complete definition and avoid recursing a lot
due to the fact that our accelerator tables will have many versions of the 
type, but only one complete one. We might not also have the complete type
and we need to deal with this correctly.

llvm-svn: 145759