With KEY and EMIT being switch words, most of the high layer can
be defined before drivers.
In addition to this change, I've compacted core blocks which were
becoming quite sparse.
This duplicated feature existed because of bootstrapping issues
with LIT", but again, with careful threading, we can clean things
up.
We can now have a proper "Collapse OS" prompt :)
Prebiously, when encountering an error during a : ; definition from
input buffer, because the input buffer wasn't flushed, we would continue
interpreting and quit the whole program when encountering ;.
