Hook up the libvorbis self test code so it is run by automake's 'check'

Hook up the libvorbis self test code so it is run by automake's 'check'
target. This only enables the sharedbook.c self test, as the codebook.c
self test has bit rotted.

Unfortunately the doc stuff scrolls the results off the screen, but
given the trouble we've had with the doc build in the past, I'm
loath to place it before the code.

svn path=/trunk/vorbis/; revision=13666