[Tremor] Tremor codebook params

[Binh Ta Quang]

Hello all,
I see that some fields in codebook unpacking does not use all of bits as
described in the Vorbis I specification! 

Examples: 
- The codebook_dimensions is coded as a 16-bit unsigned integer, but the
exact value in practice is lower 128! 
- The codebook_entries is coded as a 24-bit unsigned integer, but in
practice, it's usually about 16-bit unsigned integer!
- The vorbis_codebook_count is coded as a 8-bit unsigned integer, but
it's usually under 128 codebooks in practice! 
- ...

Are there anyone:
	- point me the value ranges of the fields are used by modern
encoders? 
	- tell me where the VQ calculation in Tremor_lowmem? 

Thanks a lot.