Fix minors in function documentation
Found while updating dvdread:
06ee6090 -> simple fix for a duplicated "to"
91ec7301 -> found while trying to implement an alternative for dvdnav_get_title_string as recomended on libdvdnav docs. DVDISOVolumeInfo should only be used as a fallback for DVDUDFVolumeInfo in case of error. In those cases DVDUDFVolumeInfo returns -1 and not 0 (success)
Edited by Miguel Borges de Freitas