CI: cleanup build warnings

Tests: fixed "unused const variable" warning
CMakeLists.txt: fixed deprecation warnings

src/p2p_server.cpp

@@ -31,7 +31,8 @@
 #include <fstream>
 #include <numeric>
 
-static constexpr char log_category_prefix[] = "P2PServer ";
+LOG_CATEGORY(P2PServer)
+
 static constexpr char saved_peer_list_file_name[] = "p2pool_peers.txt";
 static const char* seed_nodes[] = { "seeds.p2pool.io", ""};
 static const char* seed_nodes_mini[] = { "seeds-mini.p2pool.io", "" };
@@ -1049,6 +1050,11 @@ const PoolBlock* P2PServer::find_block(const hash& id) const
 	return m_pool->side_chain().find_block(id);
 }
 
+const char* P2PServer::get_log_category() const
+{
+	return log_category_prefix;
+}
+
 void P2PServer::on_timer()
 {
 	if (m_pool->stopped()) {