Bring GDC 4.10/master up to latest 4.10 GCC snapshot.

I can't guarantee that all of this is absolutely correct, but the add_to_same_comdat_group conversion is the only one I'm not that sure about. This got things compiling again on the latest GCC 4.10 snapshot.
Should be ``thunk_node->add_to_same_comdat_group (funcn);``