Fortran: ensure to remove generated modulefiles

"make distcheck" complains if we don't clean modulefiles.  A recent
commit started generating modulefiles in the ompi/mpi/fortran/mpif-h
directory, so we need to start cleaning them there, like we do in
other Fortran directories.
Merge pull request #25 from miked-mellanox/topic/sync_with_ompi

sync with ompi-release/v1.8
Fortran: do not dist mpif-h/sizeof_f.f90; it is generated
Merge pull request #137 from jsquyres/pr/fortran-dist-fixes

Two "make distcheck" fixes for Fortran
Merge remote-tracking branch 'release/v1.8' into topic/sync_with_ompi