This version uses MPI_Isend instead of the original MPI_Issend. This
leaves MPI implementations more freedom about communication details.
However it may lead to increased resource usage by the MPI implementation.

The cmdline.h is not necessary to be cleaned for regular users.
Only developers changing cmdline.ggo will need to.

This data pattern is inspired by the communication pattern in the DUNE
function BufferedCommunicator::sendRecv() from the dune-common module.