XPACKed core

Most of Collapse OS' core words are cross compiled (B390).
However, some of them are too dynamically referenced to be
cross-compiled without great pain, so we XPACK (B267) them,
that is, we put them in source form in the target's
initialization section (see B89).

These words will be compiled into RAM at initialization, which
is a bit wasteful both in RAM and in boot time, so we will
typically relink (B120) that newly compiled binary and append
it to our existing binary for optimal resource usage.

Load range: 440-446