CI: cleanup build warnings

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

src/stratum_server.cpp

@@ -23,7 +23,7 @@
 #include "params.h"
 #include "p2pool_api.h"
 
-static constexpr char log_category_prefix[] = "StratumServer ";
+LOG_CATEGORY(StratumServer)
 
 static constexpr int DEFAULT_BACKLOG = 128;
 static constexpr uint64_t DEFAULT_BAN_TIME = 600;
@@ -544,6 +544,11 @@ void StratumServer::reset_share_counters()
 	m_totalFailedShares = 0;
 }
 
+const char* StratumServer::get_log_category() const
+{
+	return log_category_prefix;
+}
+
 void StratumServer::print_stratum_status() const
 {
 	uint64_t hashes_15m, hashes_1h, hashes_24h, total_hashes;