dct_bits is never set except in h264, where it is never used, thus
remove it. Then, remove all functions that were set based on non-zero
(32) values for dct_bits. Lastly, merge 9-14 bpp functions for get_pixels
and draw_edge, which only care about pixel storage unit size, not actual
bits used (i.e. they don't clip).
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>