1.0.25.2: Eliminate untagged pointers to heap space in cold-init

1.0.25.2: Eliminate untagged pointers to heap space in cold-init

Load-time value fixups encountered by genesis are added as a kind of
toplevel form to be patched during cold-init.  The reference to the
location to fix up was being dumped as a SAP pointing to the correct
point in heap space.  Instead of dumping a SAP, we now dump the
containing object and an offset within the object, thus removing one
obstacle to running the GC or doing other heap-space relocation prior
to running the cold-toplevels.