Simplify OD_UNBIASED_RSHIFT.

Just in case the compiler can't figure it out.

Signed-off-by: Timothy B. Terriberry <tterribe@xiph.org>
Remove od_state.input
Make frame buffers explicitly aligned.
pkg-config: fix uninstalled .pc files
mcenc.c: Properly clear MVs hit cache

This avoids spurious hits when hit_bit is reset to 0.
Unfortunately this slightly increases rate on video-1-short:
           RATE (%)  DSNR (dB)
    PSNR 0.03606  -0.00193
 PSNRHVS 0.03931  -0.00311
    SSIM 0.01739  -0.00084
FASTSSIM 0.02251  -0.00138
Prepare half-pel BMA sad
do fullpell BMA search at halfpel resolution
round-to-even predictor
Actual halfpel BMA search
Disable OBMC refinement
Disable halfpel BMA refinement
hacks