[snmp] Compiler warning fixes for when "--enable-snmp" is configured.

Compiled on 32-bit and 64-bit linux gcc 4.1.2 platforms.
No run-time testing on 32-bit and limited run-time testing on 64-bit.
diff --git a/ripd/rip_snmp.c b/ripd/rip_snmp.c
index d02c761..61c47c7 100644
--- a/ripd/rip_snmp.c
+++ b/ripd/rip_snmp.c
@@ -93,10 +93,14 @@
 struct route_table *rip_ifaddr_table;
 
 /* Hook functions. */
-static u_char *rip2Globals ();
-static u_char *rip2IfStatEntry ();
-static u_char *rip2IfConfAddress ();
-static u_char *rip2PeerTable ();
+static u_char *rip2Globals (struct variable *, oid [], size_t *,
+			    int, size_t *, WriteMethod **);
+static u_char *rip2IfStatEntry (struct variable *, oid [], size_t *,
+				int, size_t *, WriteMethod **);
+static u_char *rip2IfConfAddress (struct variable *, oid [], size_t *,
+				  int, size_t *, WriteMethod **);
+static u_char *rip2PeerTable (struct variable *, oid [], size_t *,
+			      int, size_t *, WriteMethod **);
 
 struct variable rip_variables[] = 
 {
@@ -215,7 +219,7 @@
     }
 }
 
-struct interface *
+static struct interface *
 rip_ifaddr_lookup_next (struct in_addr *addr)
 {
   struct prefix_ipv4 p;