[PECOFF] Fix AMD64_ADDR64 relocation.

IMAGE_REL_AMD64_ADDR64 relocation should set 64-bit *VA* (virtual
address) instead of *RVA* (relative virtual address), so we have
to add the iamge base to the target's RVA.
Add __NSCFDictionary to the list of NSDictionary-like types for which we know to generate synthetic children