Properly initialize the DCT scratch space.
Properly initialize the DCT scratch space.

r17728 now expects this to be cleared to zero before entering
 oc_enc_block_transform_quantize(), but we weren't doing so.

svn path=/trunk/theora/; revision=17738

brion/theora,brion/theora,brion/theora,brion/theora,brion/theora