* support $no_proxy, which is a comma or space separated list of
host[:port] elements for which proxying is to be disabled.
(asked for by cgd in [bin/5027])
* if $FTPANONPASS is defined, use that as the anon ftp password
(instead of "`whoami`@")
* allow http URL's without a filename as long as an output file
is specified.
other stuff:
* implement parse_url(), which breaks up a URL into its bits, and use.
* simplify url_get() and auto_fetch() to use parse_url() and to not
modify the supplied URL or a copy of it.
* implement xmalloc() and xstrdup(); error-checked malloc()/strdup()
* add more consistency to messages, quoting strings in output as `%s'