Expressions like array[get_vlc2()] can be optimized by using a symbols
table if the array is always the same for a given VLC. This requirement
is fulfilled for several VLCs used by ATRAC3, therefore this commit
implements this. This comes without any additional costs when using
ff_init_vlc_from_lengths() as one can then remove the codes tables.

While at it, remove the arrays of pointers to the individual arrays and
put all lengths+symbol pairs in one big array.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>