If MPI extensions are enabled, all
`ompi/mpiext/pcollreq/use-mpi/mpiext_*_usempi.h` are included in
`ompi/mpi/fortran/mpiext-use-mpi/mpi-ext-module.F90` and all
`ompi/mpiext/pcollreq/use-mpi/mpiext_*_usempif08.h` are included in
`ompi/mpi/fortran/mpiext-use-mpi-f08/mpi-f08-ext-module.F90` using
`#include` directives.
In `mpiext_*_usempi.h` and `mpiext_*_usempif08.h`, some MPI extension
may want to use constants or handles defined in the `mpi` module and
the `mpi_f08` module. For example, if you want to define a new
datatype in `mpi_f08_ext`, you'll need the definition of
`type(mpi_datatype)`. However, putting `use mpi_f08` line in thier
`mpiext_*_usempif08.h` may cause a compilation error if more than
one MPI extensions are enabled because the `use` statement must be
put prior to any variable declarations.
To resolve this problem, this commit puts `use mpi` and `use mpi_f08`
as first lines of `mpi-ext-module.F90` and `mpi-f08-ext-module.F90`
respectively.
Signed-off-by: KAWASHIMA Takahiro <t-kawashima@jp.fujitsu.com>