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