File names with "funny" characters get translated wrong by
pathname2url (any variety).  E.g. the (Unix) file "/ufs/sjoerd/#tmp"
gets translated into "/ufs/sjoerd/#tmp" which, when interpreted as a
URL is file "/ufs/sjoerd/" with fragment ID "tmp".

Here's an easy fix.  (An alternative fix would be to change the
various implementations of pathname2url and url2pathname to include
calls to quote and unquote.

[The main problem is with the normal use of URLs:
	url = url2pathname(file)
	transmit url
	url, tag = splittag(url)
	urlopen(url)
]

In addition, this patch fixes some uses of unquote:
- the host part of URLs should be unquoted
- the file path in the FTP URL should be unquoted before it is split
  into components.
- because of the latter, I removed all unquoting from ftpwrapper,
  and moved it to the caller, but that is not essential