* While DIRECTORY on local UNC paths worked as of 22.214.171.124, turns
out Windows network shares don't exist as far as stat() is
concerned -- and hence using the proper share path didn't work.
Replace QUERY-FILE-SYSTEM in MAP-DIRECTORY with UNIX-REALPATH
sans stat, and we're good.
* Canonicalize the pathnames for DIRECTORY, so that (DIRECTORY #P".")
is equivalent to (DIRECTORY #P"./") -- ditto for #P".." and
#P"../". Also make DIRECTORY treat :UNSPECIFIC names and types as
if they were NIL.