message: gltfpack: Optimize empty mesh filtering
  This is now carefully avoiding extra large allocations by swapping
  vectors (we can't use std::move since the code must compile with C++98).
diff: @@ -848,11 +848,16 @@ void filterEmptyMeshes(std::vector<Mesh>& meshes)
  if (i != write)
  {
  - // note: this copy is expensive; we could use move in C++11 or swap manually which is a bit painful...
  - meshes[write] = mesh;
  + // the following code is roughly equivalent to meshes[write] = std::move(mesh)
  + std::vector<Stream> streams;
  + streams.swap(mesh.streams);
  - mesh.streams.clear();
  - mesh.indices.clear();
  + std::vector<unsigned int> indices;
  + indices.swap(mesh.indices);
  +
  + meshes[write] = mesh;
  + meshes[write].streams.swap(streams);
  + meshes[write].indices.swap(indices);
  }
  write++;
  