This is done by adding a "C<* override" layer that is reset to 0 on
ABORT.
The problem was that when ABORT happened during a LOAD, we had a
resetted RSP and started from a clean INTERPRET, but LOAD didn't
have the opportunity to restore C<*, which caused it to continue
interpreting from the faulty BLK.
With a C<* override, we don't need to *restore* C<*, we just need to
clear the override.