Fix unit test code to work with boost::detail::atomic_count.

asio/src/tests/unit/unit_test.hpp

diff --git a/asio/src/tests/unit/unit_test.hpp b/asio/src/tests/unit/unit_test.hpp
index fb4bd1c..77d8645 100644
--- a/asio/src/tests/unit/unit_test.hpp
+++ b/asio/src/tests/unit/unit_test.hpp
@@ -52,7 +52,7 @@
 
 inline atomic_count& test_errors()
 {
-  static atomic_count errors;
+  static atomic_count errors(0);
   return errors;
 }