Based on extensive discussions before/at the June 2014 developer's
meeting, put a lengthy comment explaining a second reason why we
''must'' use an RTE barrier during MPI_FINALIZE and
MPI_COMM_DISCONNECT (i.e., unreliable transports). Slightly explain
more the original reason why we do this, too (BTLs can lie/buffer a
message without actually injecting it on the network).
This commit was SVN r32095.
8e52ba423f