smux: drop findVar element from trap object struct

This element was not unused.
diff --git a/lib/smux.h b/lib/smux.h
index 78460e6..b7d5096 100644
--- a/lib/smux.h
+++ b/lib/smux.h
@@ -47,8 +47,7 @@
 
 struct trap_object
 {
-  FindVarMethod *findVar;
-  int namelen;
+  int namelen; /* Negative if the object is not indexed */
   oid name[MAX_OID_LEN];
 };