[cleanup] functions taking no args should be declared with void args

Use Ansi-C prototypes rather than old K&R method of declaring
function without arguments
diff --git a/bgpd/bgp_snmp.c b/bgpd/bgp_snmp.c
index 0f44e68..1e37f26 100644
--- a/bgpd/bgp_snmp.c
+++ b/bgpd/bgp_snmp.c
@@ -882,7 +882,7 @@
 }
 
 void
-bgp_snmp_init ()
+bgp_snmp_init (void)
 {
   smux_init (bm->master);
   REGISTER_MIB("mibII/bgp", bgp_variables, variable, bgp_oid);