Allow flexible stdin routing to COMM_SPAWN'ed jobs

[ompiteam]

Related to but slightly different than https://svn.open-mpi.org/trac/ompi/ticket/1050:

When we COMM_SPAWN, where does stdin for the child process come from? I think that there should be [at least] 4 options (selectable via MPI_Info keys):

1. Get stdin from the HNP. Note that this is a bit weird: any stdin from the HNP will be sent to '''both''' the parent job ''and'' the child job.
2. Get the stdout from the single parent process who called orte_spawn. This would be like standard unix pipes, a la "foo | bar", where foo's output is sent to the input of bar.
3. Get the stdout from the entire parent job who called orte_spawn. This is similar to the previous option, but note that ''all'' stdout from the entire job will be sent to the stdin in the child.
4. Have stdin tied to /dev/null. This is effectively what happens in OMPI <=v1.2, so I think that this should be the default.

Note that I didn't mention ''where'' in the child job the stdin flows -- it could be just to vpid 0, or it could be to one or more other processes, or ... I think that's what ticket https://svn.open-mpi.org/trac/ompi/ticket/1050 is about, and is a slightly different issue than this ticket.

[ompiteam]

Imported from trac issue 1185. Created by jsquyres on 2007-11-07T12:52:58, last modified: 2008-05-29T20:13:37

[ompiteam]

Trac comment by jsquyres on 2008-05-29 20:13:37:

This won't happen for v1.3.

[rhc54]

Done long ago