Fix VirtualFileQt::seek return value
The libsndfile docu says
sf_vio_seek
typedef sf_count_t (*sf_vio_seek) (sf_count_t offset, int whence, void *user_data) ;
The virtual file context must seek to offset using the seek mode provided by whence which is one of SEEK_CUR, SEEK_SET, SEEK_END.
The return value must contain the new offset in the file.
Edited by Albert Astals Cid