mcenc.c: Skip the 4MV SATD in speed level 2.  2% speedup.  Avoid duplicating the first set b candidate (correctly adding the surrounding accelerators hurt efficiency).
mcenc.c: Skip the 4MV SATD in speed level 2.  2% speedup.  Avoid duplicating the first set b candidate (correctly adding the surrounding accelerators hurt efficiency).

svn path=/trunk/theora/; revision=17507

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