Remove useless extern for environ

This commit was SVN r5364.

src/communicator/comm_dyn.c

@@ -46,7 +46,6 @@
 
 #include "runtime/runtime.h"
 #include "util/printf.h"
-extern char **environ;
 
 int ompi_comm_connect_accept ( ompi_communicator_t *comm, int root,
                                orte_process_name_t *port, int send_first,