o Add fexists word to check for the presence of a file
o make fexists and fload immediate words which DTRT both interpreted
and compiled (doh!)
o add an init word which gets run at bootstrapping time to do extra
post-coldload initialization (in the default implementation, we
look for /boot/boot.4th and load it if found).
to the Forth interpreter. Instantiate all of our inbuilt commands
as Forth words, and handle them being called from there.
Add my copyright to the bcache module (oops).
