Remove purely internal variable from exported symbols.

src/xt_mpi.c

@@ -680,7 +680,7 @@ xt_mpi_generate_compact_datatype(const int *disp, int disp_len,
 }
 
 /* functions to handle optimizations on communicators */
-int xt_mpi_comm_internal_keyval;
+static int xt_mpi_comm_internal_keyval;
 
 typedef unsigned long used_map_elem;
 

src/xt_mpi_internal.h

@@ -68,8 +68,6 @@ enum xt_mpi_tags {
 };
 
 
-extern int xt_mpi_comm_internal_keyval;
-
 PPM_DSO_INTERNAL void
 xt_mpi_init(void);
 PPM_DSO_INTERNAL void