Make fancy inspector more robust w.r.t. unexpected logical PATHNAME-HOST

While CLHS seems to guarantee PATHNAME-HOST to return a string, this is
not always the case in practice (e.g. SBCL returns a
SB-IMPL:LOGICAL-HOST instance).

* swank-fancy-inspector.lisp (emacs-inspect logical-pathname): wrap the
  return value of PATHNAME-HOST in a (:value ...) in case it is not a
  string