just flushing the pile:
- get rid of Put4 in dsp.c
- move LD4 enum value
- move more fields and code under the ONLY_KEYFRAME_CODE compile flag
- update test_ref.ppm reference (now with FANCY_UPSCALER)
- simplify VP8GetSignedValue()
- use HE and VE naming for prediction mode instead of H and V
- some missing c89 fixes
- code style nits
all test vectors still passing
