Removing the complaint about the attribute functions when we compile a C++ file.

Second level commit log: "The Great and Powerful Jeff Squyres figured out and fixed this bug remotely. All praise Jeff." ;) yup yup

This commit was SVN r2304.

include/mpi.h

@@ -317,6 +317,9 @@ enum {
 #define MPI_WIN_DUP_FN OMPI_C_MPI_WIN_DUP_FN
 #endif
 
+#if defined(c_plusplus) || defined(__cplusplus)
+extern "C" {
+#endif
 int OMPI_C_MPI_TYPE_NULL_DELETE_FN( MPI_Datatype datatype, int type_keyval,
                                     void* attribute_val_out, void* flag );
 int OMPI_C_MPI_TYPE_NULL_COPY_FN( MPI_Datatype datatype, int type_keyval, 
@@ -351,6 +354,10 @@ int OMPI_C_MPI_WIN_DUP_FN( MPI_Win window, int win_keyval, void* extra_state,
                            void* attribute_val_in, void* attribute_val_out,
                            int* flag );
 
+#if defined(c_plusplus) || defined(__cplusplus)
+}
+#endif
+
 /*
  * External variables
  */