Fix C++20 compatibility: replace deprecated std::result_of and fix std::max type mismatch

include/svm/enhanced_engine.h

@@ -67,7 +67,7 @@ class EnhancedExecutionEngine : public ExecutionEngine {
         ~ThreadPool();
 
         template<typename F>
-        auto enqueue(F&& f) -> std::future<typename std::result_of<F()>::type>;
+        auto enqueue(F&& f) -> std::future<typename std::invoke_result_t<F>>;
 
         void shutdown();
 

src/svm/enhanced_engine.cpp

@@ -308,9 +308,9 @@ EnhancedExecutionEngine::ThreadPool::~ThreadPool() {
 
 template<typename F>
 auto EnhancedExecutionEngine::ThreadPool::enqueue(F&& f) 
-    -> std::future<typename std::result_of<F()>::type> {
+    -> std::future<typename std::invoke_result_t<F>> {
 
-    using return_type = typename std::result_of<F()>::type;
+    using return_type = typename std::invoke_result_t<F>;
 
     auto task = std::make_shared<std::packaged_task<return_type()>>(
         std::forward<F>(f)

src/svm/spl_programs.cpp

@@ -300,7 +300,7 @@ ExecutionOutcome ExtendedSystemProgram::handle_initialize_nonce(
     ProgramAccount& nonce_account = context.accounts[nonce_account_key];
     nonce_account.program_id = EXTENDED_SYSTEM_PROGRAM_ID;
     nonce_account.executable = false;
-    nonce_account.lamports = std::max(nonce_account.lamports, 1447680UL); // Rent-exempt
+    nonce_account.lamports = std::max(nonce_account.lamports, static_cast<Lamports>(1447680UL)); // Rent-exempt
     nonce_account.rent_epoch = context.current_epoch;
 
     // Initialize nonce account data