New default coefficient/band probabilities.
Gives 0.5-0.6% improvement on derf and stdhd, and 1.1% on hd. The old tables basically derive from times that we had only 4x4 or only 4x4 and 8x8 DCTs. Note that some values are filled with 128, because e.g. ADST ever only occurs as Y-with-DC, as does 32x32; 16x16 ever only occurs as Y-with-DC or as UV (as complement of 32x32 Y); and 8x8 Y2 ever only has 4 coefficients max. If preferred, I can add values of other tables in their place (e.g. use 4x4 2nd order high-frequency probabilities for 8x8 2nd order), so that they make at least some sense if we ever implement a larger 2nd order transform for the 8x8 DCT (etc.), please let me know Change-Id: I917db356f2aff8865f528eb873c56ef43aa5ce22