Generic: use compat_urllib_parse_unquote to prevent utf8 mangling

Generic: use compat_urllib_parse_unquote to prevent utf8 mangling
of the entire page in python 2.

-requires- fixed compat_urllib_parse_unquote

example - the following will save with a mangled playlist title,
 instead of the kanji for 'tsunami'. This affects all utf8encoded
 urls as well

youtube-dl -f18 -o '%(playlist_title)s-%(title)s.%(ext)s' \
  https://gist.githubusercontent.com/atomicdryad/fcb97465e6060fc519e1/raw/61c14c1e3a4985471dcf56c281d24d7e781a4e0e/tsunami.html