[STUMP] pathname-is-executable-p for SBCL

[Ben Spencer]

The new implementation of pathname-is-executable-p for SBCL appears to
have broken things by changing (sb-int:unix-namestring pathname) to
(file-namestring pathname).  The latter converts eg /bin/ls to ls, so
it will only work for files in the cwd.

The problem is not immediately noticeable because of the path cache,
but if you do (setf *path-cache* nil) you should see that path
completion is broken.

I'm not just posting a patch in case there was a subtle reason for the
change (unix-namestring being deprecated or something?).


Ben