bug 153, 1066: Convert XBEL bookmarks to/from UTF-8.
When the file is being read, Expat provides the strings to ELinks in
UTF-8, so ELinks can put them in struct bookmark without conversions.
Make sure gettext returns any placeholder strings in UTF-8, too.
Replace '\r' with ' ' in bookmark titles and URLs.
When the file is being written, put encoding="UTF-8" in the XML
declaration, and then write out the strings from struct bookmark
without character set conversions. Do replace some characters
with entity references though, by calling add_html_to_string().