Port r16328 and r16330 from libvorbis.

ivorbisfile_example.c ignores an error code and plows ahead blindly if
 libvorbisidec reports the current bitstream section is bad (OV_EBADLINK).
Retrying after the error crashes libvorbisidec due to the unitialized state.


git-svn-id: https://svn.xiph.org/trunk/Tremor@17526 0101bb08-14d6-0310-b084-bc0e0c8e3800