Stable ABI

Across all architectures, some offset are referred to by off-
sets that don't change (well, not without some binary manipu-
lation). Here's the complete list of these references:

04 BOOT addr         06 (uflw) addr      08 LATEST
42 EXIT wordref      53 (br) wordref     67 (?br) wordref
80 (loop) wordref    a9 2>R wordref      bf (n) wordref
d4 (s) wordref

BOOT and (uflw) exist because they are referred to before those
words are defined (in core words). LATEST is a critical part
of the initialization sequence.

                                                        (cont.)