move openmpi/ompi/mpiext/FOO/c/mpiext_FOO_c.h to
openmpi/ompi/mpiext/FOO_c.h in order to use consistent
paths with mpif.h extensions
Refs. open-mpi/ompi#6019
Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>
Until the MPI Forum decides to add the persistent collective
communication request feature to the MPI Standard, these functions
are supported through MPI extensions with the `MPIX_` prefix.
Only C bindings are supported currently.
Signed-off-by: KAWASHIMA Takahiro <t-kawashima@jp.fujitsu.com>
