uiop/stream:call-with-temporary-file docstring incorrect

[pipping]

The docstrings for

  uiop/stream:call-with-temporary-file and
  uiop/stream:stream:with-temporary-file

both mention that `prefix` defaults to "uiop". This does not seem to be the case. In fact, `prefix` does not have a default according to the signature of `uiop/stream:call-with-temporary-file`.

In practice, however (and this is what the documentation should probably say instead), the function behaves almost as if the default was "tmp" since the expression `(or prefix "tmp")` is used to construct the variable `prefix-pn`, which is the only value influenced by prefix. The key difference between an actual default value of `prefix` and this behaviour is that the current implementation turns even an explicitly passed `nil` into "tmp".

[Faré (fahree)]

Thanks! Fixed in 176ab37.