MPI 4.1 - MPI_COMM_DUP and error handlers

[hppritcha]

Need to check if Open MPI is currently duplicating error handlers onto a new communicator created via MPI_COMM_DUP.

See entry 9 in section B 1.1 of the MPI-4.1 standard

[hppritcha]

MPI_Comm_dup and friends (with info) eventually call ompi_comm_set_nb in which the errhandler of the input communicator is copied to the new communicator structure and a ref is taken on the error handler. So it appears OMPI is already doing the right thing here.