dnxhddec: use unsafe bitstream reader

Each line is padded by the format, and errors are now reported and
stop the decoding. Around 5% speedup.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/dnxhddec.c

@@ -26,6 +26,7 @@
 #include "libavutil/timer.h"
 #include "avcodec.h"
 #include "blockdsp.h"
+#define  UNCHECKED_BITSTREAM_READER 1
 #include "get_bits.h"
 #include "dnxhddata.h"
 #include "idctdsp.h"