Avoid deprecated Boost.Asio interfaces

Change-Id: I00d285893ff61619f49dff8a8a55d0d0e2c309a7
diff --git a/tests/unit/util/regex.t.cpp b/tests/unit/util/regex.t.cpp
index d09688e..07ec293 100644
--- a/tests/unit/util/regex.t.cpp
+++ b/tests/unit/util/regex.t.cpp
@@ -279,7 +279,7 @@
 {
   auto backRef = make_shared<RegexBackrefManager>();
   auto cm = make_shared<RegexBackrefMatcher>("(<a><b>)", backRef);
-  backRef->pushRef(static_pointer_cast<RegexMatcher>(cm));
+  backRef->pushRef(std::static_pointer_cast<RegexMatcher>(cm));
   cm->compile();
   bool res = cm->match(Name("/a/b/c"), 0, 2);
   BOOST_CHECK_EQUAL(res, true);