Include and test system_error.hpp in warnings_test

test/warnings_test.cpp

@@ -18,6 +18,7 @@
 #pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
 #endif
 
+#include <boost/system/system_error.hpp>
 #include <boost/system/error_code.hpp>
 #include <boost/core/lightweight_test.hpp>
 #include <cerrno>
@@ -42,5 +43,10 @@ int main()
 
     BOOST_TEST( bc == bn );
 
+    boost::system::system_error x( bc, "what_arg" );
+
+    BOOST_TEST_EQ( x.code(), bc );
+    BOOST_TEST_CSTR_EQ( x.what(), "what_arg" );
+
     return boost::report_errors();
 }