Annoying file-system "stub" functions

When what's now OpenMCL was first ported to VxWorks/LinuxPPC, a number
of MCL-specific file-system functions (CCL:DIRECTORYP, until recently
CCL:COPY-FILE, CCL:LOCK-FILE, others ?) were left largely undefined
(they just call BREAK when called.)

There's a bit more filesystem and FFI infrastructure in OpenMCL now
than there was then; these things should all be found and cleaned up.

Most or all of these things would behave a bit differently in OpenMCL
than they did in MCL; some of them might behave differently on
differently platforms (e.g., Jaguar implemens lockf, but documents
it as providing "advisory" locking.)