Fix import error when the path of a video contains Japanese characters.

Qt4 doesn't handle strings as UTF-8 in the default settings. According to VideoLan's documentation[1], it says "As a general rules, all character strings passed to LibVLC should be in UTF-8."
Therefore, by setting QTextCodec::setCodecForCStrings, Qt4 will use UTF-8 and the import error will be fixed.

References:
[1] https://wiki.videolan.org/Documentation:Unicode/



Signed-off-by: Hugo Beauzée-Luyssen <hugo@beauzee.fr>