fix ave/spatial

Dear Axel ,

​The NOTE section of fix ave/spatial needs to be modified !

The fix ave/spatial command has been replaced by the more flexible fix ave/chunk and compute chunk/atom commands. The fix ave/spatial command will be removed from LAMMPS sometime in the summer of 2015.

Thanks .

As of LAMMPS version 31 May 2016 fix ave/spatial and its derivative
fix ave/spatial/sphere are removed from LAMMPS.