converter from mysql-double-utf8 to regular utf8
compile with gcc
then use it with your SQL dump like this
./a.out my-sql-dump.sql new-sql-dump.sql
you will end up with a SQL dump that has proper utf8 encoding. Import that dump into your database and you're done.
in some configurations mysqldump will put localized comments in your original dump. better remove all SQL comments (lines starting with --) before converting.