Additional codebook validity checks.

Bail out of codebook loading early if the packet doesn't have enough data for
 the size of the codebooks it asked for.
This doesn't in and of itself provide any additional security, but it does make
 peak heap usage on many invalid files smaller.


git-svn-id: https://svn.xiph.org/trunk/Tremor@17539 0101bb08-14d6-0310-b084-bc0e0c8e3800