Tidy up some warnings

example/echo-op/echo_op.cpp

@@ -361,7 +361,6 @@ int main(int argc, char** argv)
     auto const address{net::ip::make_address(argv[1])};
     auto const port{static_cast<unsigned short>(std::atoi(argv[2]))};
 
-    using socket_type = net::ip::tcp::socket;
     using endpoint_type = net::ip::tcp::endpoint;
 
     // Create a listening socket, accept a connection, perform

test/beast/core/rate_policy.cpp

@@ -9,6 +9,7 @@
 
 // Test that header file is self-contained.
 #include <boost/beast/core/rate_policy.hpp>
+#include <boost/core/ignore_unused.hpp>
 
 #include <boost/beast/_experimental/unit_test/suite.hpp>
 
@@ -21,8 +22,8 @@ public:
     void
     run() override
     {
-        unlimited_rate_policy{};
-        simple_rate_policy{};
+        boost::ignore_unused(unlimited_rate_policy{});
+        boost::ignore_unused(simple_rate_policy{});
 
         pass();
     }