Wow, that was unexpectedly painless – even for TH03 where we have to
deal with a significant number of un-RE'd pieces of data. And for TH04
and TH05, it turns out that we not only *want* to move the entire _TEXT
segment into the new unit to keep the amount of `extern` declarations
to a minimum, but in fact *have* to because of graph_putsa_fx()'s fancy
labels in the data segment.
Part of P0263, funded by [Anonymous].