Duplicated functions for writing/parsing of prediction weight table

[ksuehring]

Prediction weight table reading and parsing uses different functions for parsing and writing depending on the location in PH or SH, although the same syntax table in the specification text is referenced in both locations in the spec text:

  void  parsePredWeightTable( Slice* pcSlice, const SPS *sps );
  void parsePredWeightTable ( PicHeader *picHeader, const SPS *sps );

  void xCodePredWeightTable     ( Slice* pcSlice );
  void xCodePredWeightTable     ( PicHeader *picHeader, const SPS *sps );

Code should be refactored to avoid duplication.

Cleanup for variable naming is needed as well.