UIOP API

[Robert Goldman]

In a recent ticket, Faré writes:

"Some things are defined in uiop/pathname and used in uiop/filesystem,
so exporting them is the right thing. There is currently no notion of
"shared within uiop but not exported outside uiop". I suppose you could
make do using package::qualifiers and/or import statements. Meh."

Looking at the UIOP code, I see that there is no equivalent of
ASDF/INTERFACE.

Should we add this?  I have the feeling that might be "Should we add
this, before it's too late?"

Comments welcome,
r