Fix tests run with make check when using alternative allocators.
The call to free in line 584 of sharedbook.c mismatches the _ogg_calloc call used to allocated that data in line 216. This causes make check to fail when alternative allocators are used, e.g. the xmm_malloc family of allocators used with the Lancer optimizations. Signed-off-by: Ralph Giles <firstname.lastname@example.org>