All 'failure' style returns are <0; this either indicates a generic
'false' value (eg, ready?  T or F) or an error condition.  Code can
safely just test for < 0, or look at the specific return code for more
detail.

---------- (internal calls) ------------


long _get_next_page()
    OV_FALSE, OV_EOF, OV_EREAD	

long _get_prev_page()
    OV_EREAD, OV_FAULT

int _bisect_forward_serialno()
    OV_EREAD

int _fetch_headers()
    OV_EREAD, OV_ENOTVORBIS, OV_EVERSION, OV_EBADHEADER

int _open_seekable()    
    OV_EREAD, OV_ENOTVORBIS, OV_EVERSION, OV_EBADHEADER, OV_FAULT
	+ ov_raw_seek

int _open_nonseekable()
    OV_EREAD, OV_ENOTVORBIS, OV_EVERSION, OV_EBADHEADER

int _process_packet()
    OV_EOF, OV_HOLE, OV_EBADLINK

---------- public calls ------------

int vorbis_analysis_headerout()
    OV_EIMPL

int vorbis_analysis_wrote()
    OV_EINVAL

int vorbis_synthesis_headerin()
    OV_ENOTVORBIS, OV_EVERSION, OV_EBADHEADER

int vorbis_synthesis()
    OV_ENOTAUDIO, OV_EBADPACKET

int vorbis_synthesis_read()
    OV_EINVAL

int ov_open_callbacks()   
    OV_EREAD, OV_ENOTVORBIS, OV_EVERSION, OV_EBADHEADER, OV_FAULT

int ov_open()
    OV_EREAD, OV_ENOTVORBIS, OV_EVERSION, OV_EBADHEADER, OV_FAULT

long ov_bitrate()
    OV_EINVAL, OV_FALSE

long ov_bitrate_instant()
    OV_FALSE

ogg_int64_t ov_raw_total()
    OV_EINVAL

ogg_int64_t ov_pcm_total()
    OV_EINVAL

double ov_time_total()
    OV_EINVAL

int ov_raw_seek()
    OV_ENOSEEK, OV_EINVAL, OV_BADLINK

int ov_pcm_seek_page()
    OV_ENOSEEK, OV_EINVAL, OV_EREAD, OV_BADLINK, OV_FAULT

int ov_pcm_seek()
    OV_ENOSEEK, OV_EINVAL, OV_EREAD, OV_BADLINK, OV_FAULT

int ov_time_seek()
    OV_ENOSEEK, OV_EINVAL, OV_EREAD, OV_BADLINK, OV_FAULT

int ov_time_seek_page()
    OV_ENOSEEK, OV_EINVAL, OV_EREAD, OV_BADLINK, OV_FAULT