message: vertexcodec: Added avgbits statistic
  maxbits reflects sudden spikes that can happen once in the entire block
  but don't communicate the expected size (modulo internal blocking
  rounding) well. With avgbits 2.5 with a good encoding the hope is we
  can get around 3-4 bits even if maxbits is 8.
diff: @@ -59,6 +59,7 @@ static void traceEncodeVertexBlock(const unsigned char* vertex_data, size_t vert
  int uniq[256] = {};
  int max[256] = {};
  int orv[256] = {};
  + int sumb[256] = {};
  bool uniqb[256][256] = {};
  for (size_t i = 1; i < vertex_count; ++i)
  @@ -101,6 +102,8 @@ static void traceEncodeVertexBlock(const unsigned char* vertex_data, size_t vert
  orv[k] |= delta;
  + sumb[k] += bits(delta);
  +
  #if TRACE > 1
  printf("%02x/%02x ", vertex_data[vertex_offset], delta);
  #endif
  @@ -149,6 +152,11 @@ static void traceEncodeVertexBlock(const unsigned char* vertex_data, size_t vert
  printf("| maxbits\n");
  + for (size_t k = 0; k < vertex_size; ++k)
  + printf("%3.1f ", double(sumb[k]) / double(vertex_count - 1));
  +
  + printf("| avgbits\n");
  +
  for (size_t k = 0; k < vertex_size; ++k)
  printf("%d ", bitsset(orv[k]));
  