to-be-squashed: make MPIR_F08_MPI_IN_PLACE etc visible

Apparently, the C binding linkage in fortran module is when linking user
programs.

src/binding/fortran/use_mpi_f08/wrappers_c/utils.c

@@ -6,14 +6,14 @@
 #include "cdesc.h"
 #include <string.h>
 
-int MPIR_F08_MPI_IN_PLACE;
-int MPIR_F08_MPI_BOTTOM;
+int MPIR_F08_MPI_IN_PLACE MPICH_API_PUBLIC;
+int MPIR_F08_MPI_BOTTOM MPICH_API_PUBLIC;
 
 /* MPI_F08_STATUS_IGNORE and MPI_F08_STATUSES_IGNORE are required by MPI-3.0.
  * the obj variables are linked in mpi_f08_link_constants module via bind(c).
  */
-MPI_F08_status MPIR_F08_MPI_STATUS_IGNORE_OBJ;
-MPI_F08_status MPIR_F08_MPI_STATUSES_IGNORE_OBJ[1];
+MPI_F08_status MPIR_F08_MPI_STATUS_IGNORE_OBJ MPICH_API_PUBLIC;
+MPI_F08_status MPIR_F08_MPI_STATUSES_IGNORE_OBJ[1] MPICH_API_PUBLIC;
 
 MPI_F08_status *MPI_F08_STATUS_IGNORE = &MPIR_F08_MPI_STATUS_IGNORE_OBJ;
 MPI_F08_status *MPI_F08_STATUSES_IGNORE = &MPIR_F08_MPI_STATUSES_IGNORE_OBJ[0];