MPI-4: Bogus typedef and missing definitions and routines related to `MPI_Session`

[dalcinl]

I'm using branch v5.0.x from git. The changelog claims support for MPI_Session, however I found the following issues:

• The installed mpi.h header file contains the following line:

typedef int (MPI_Session_delete_attr_function)(MPI_Session, int, void *, void *);

To the best of my knowledge, such typedef is not defined in the MPI-4 standard document. If this typedef comes from an errata or some planned extension, then I apologize for the noise, although I should note it is a bit surprising not seeing a companion MPI_Session_copy_attr_function typedef.

• The following routines are missing:

  1. MPI_Session_set_errhandler
  2. MPI_Session_get_errhandler
  3. MPI_Session_call_errhandler

  Note however that MPI_Session_create_errhandler is available.

• The MPI_ERR_SESSION error class is missing (MPI-4, pp. 472, ln. 28). It should be used for in all of the MPI_Session_XXX routines to signal an invalid MPI_Session argument.

• The MPI_Info_create_env routine is missing.
  Although not strictly related to the MPI_Session type, the MPI_Info_create_env routine is the way to get something equivalent to MPI_INFO_ENV when using the Session model (MPI-4, pp. 484, ln. 35)

[hppritcha]

related to #7993

[dalcinl]

This issue should be labeled as MPI-4.0.