core: add a facility to execute functions on the RIB io_service

refs #4279

Change-Id: I29222053348e5d1737d47c85a59d29280b4b791b
diff --git a/tests/limited-io.hpp b/tests/limited-io.hpp
index 4891b8a..a42a797 100644
--- a/tests/limited-io.hpp
+++ b/tests/limited-io.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2014-2015,  Regents of the University of California,
+/*
+ * Copyright (c) 2014-2018,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -35,6 +35,8 @@
 namespace tests {
 
 /** \brief provides IO operations limit and/or time limit for unit testing
+ *
+ *  \warning LimitedIo is incompatible with RibIoFixture
  */
 class LimitedIo : noncopyable
 {