refs #5368 make db-insert mark things unused in a less offensive way to clang

git-svn-id: file:///svn/toku/tokudb@48192 c7de825b-a66e-492c-adef-691d508d4ae1

examples/db-insert.c

@@ -79,7 +79,7 @@ static void do_prelock(DB* db, DB_TXN* txn) {
         int r = db->pre_acquire_table_lock(db, txn);
         assert(r==0);
 #else
-	db = db; txn = txn;
+	(void) db; (void) txn;
 #endif
     }
 }