convert/darcs: support changelogs with bytes 0x7F-0xFF (issue2411) This is a followup to 4481f8a93c7a, which only fixed the conversion of patches with UTF-8 metadata. This patch allows a changelog to have any bytes with values 0x7F-0xFF. It parses the XML changelog as Latin-1 and uses converter_source.recode() to decode the data as UTF-8/Latin-1. Caveats: - Since the convert extension doesn't provide any way to specify the source encoding, users are still limited to UTF-8 and Latin-1. - etree will still complain if the changelog has bytes with values 0x00-0x19. XML only allows printable characters.