464 - reply broken in channel 'write'

How did this work until now? The reply was being treated as a label, and
if 'write' returned nothing it would still work fine because the output
is already present, and a missing 'reply' leaves oargs as-is.

Should we do something to catch this? Perhaps we should track args
modified and check that there are oargs for them. But that seems quite
heavyweight.. Maybe we should clear oargs when missing a 'reply'?
465
466
467 - 'convert-names' now supports space metadata

To inform it about space metadata you have to tag environments with the
function that generated them. Every function can only ever be called
with environments generated by a single function. As an assembly-like
language, mu requires closures to be called with an explicit
environment, but it warns when the environment might not be what the
function expects.
468 - slice test time by 65%

We achieve this by separating out the freezing of system software, which
we needed to do anyway to address the duplication in 'init-fn'.