snmp: fix warnings

batch-fix all warnings that come up when enabling AgentX SNMP support.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/lib/smux.h b/lib/smux.h
index 02e9630..dc91cac 100644
--- a/lib/smux.h
+++ b/lib/smux.h
@@ -55,8 +55,8 @@
 
 /* Declare SMUX return value. */
 #define SNMP_LOCAL_VARIABLES \
-  static long snmp_int_val; \
-  static struct in_addr snmp_in_addr_val;
+  static long snmp_int_val __attribute__ ((unused)); \
+  static struct in_addr snmp_in_addr_val __attribute__ ((unused));
 
 #define SNMP_INTEGER(V) \
   ( \
@@ -108,7 +108,7 @@
 		      const struct trap_object *, size_t,
 		      u_char);
 
-extern int oid_compare (oid *, int, oid *, int);
+extern int oid_compare (const oid *, int, const oid *, int);
 extern void oid2in_addr (oid [], int, struct in_addr *);
 extern void *oid_copy (void *, const void *, size_t);
 extern void oid_copy_addr (oid [], struct in_addr *, int);