Use C++11 mutexes only (remove compat code) (#5922)

* Fix event LINT & remove default constructor/destructors
* remove compat code & modernize autolock header

src/client/clientlauncher.cpp

@@ -657,7 +657,7 @@ void ClientLauncher::speed_tests()
 		infostream << "Around 5000/ms should do well here." << std::endl;
 		TimeTaker timer("Testing mutex speed");
 
-		Mutex m;
+		std::mutex m;
 		u32 n = 0;
 		u32 i = 0;
 		do {

src/client/tile.cpp

@@ -417,7 +417,7 @@ private:
 	// Maps a texture name to an index in the former.
 	std::map<std::string, u32> m_name_to_id;
 	// The two former containers are behind this mutex
-	Mutex m_textureinfo_cache_mutex;
+	std::mutex m_textureinfo_cache_mutex;
 
 	// Queued texture fetches (to be processed by the main thread)
 	RequestQueue<std::string, u32, u8, u8> m_get_texture_queue;