swift234

Fill in _objc_empty_cache and _objc_empty_vtable.

The ObjC ABI requires these class fields to be initialized by
resolving symbols from the runtime.  So this is a historical
requirement.  Note that there is a desire to optimize this
even for ObjC, because in a project with many classes, these
can actually end up representing a significant fraction of
the external non-lazy relocations in the linked image.  But
for now we follow the spec, as we must.
The ObjC ABI requires these to be taken from the runtime,
although there is an effort to make them not require external
relocations like this, since in large projects it can actually
add up to a large percentage of the non-lazy external relocs.
3,6d
2i

Swift SVN r3804