vorbiscomment should allow for delimiter other than newline

When vorbiscomment reads from a file, it would be nice if it could use a delimiter other than newline. That way a metadata field value could have a newline (which is the case for lyrics, for instance).

I wrote a patch that does just that. I tested it on version 1.2, but it seems that newer versions of vorbiscomment don't change anything significant.