pthread -> std::thread (3/7) - Replace pthread in other engine files

MapGenerator, TextureConverter, and some other files used pthread.

Differential Revision: https://code.wildfiregames.com/D1917
This was SVN commit r22649.

source/lib/timer.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2010 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -82,16 +82,15 @@ void timer_LatchStartTime()
 #endif
 }
 
-static pthread_mutex_t ensure_monotonic_mutex = PTHREAD_MUTEX_INITIALIZER;
+static std::mutex ensure_monotonic_mutex;
 // NB: does not guarantee strict monotonicity - callers must avoid
 // dividing by the difference of two equal times.
 static void EnsureMonotonic(double& newTime)
 {
-	pthread_mutex_lock(&ensure_monotonic_mutex);
+	std::lock_guard<std::mutex> lock(ensure_monotonic_mutex);
 	static double maxTime;
 	maxTime = std::max(maxTime, newTime);
 	newTime = maxTime;
-	pthread_mutex_unlock(&ensure_monotonic_mutex);
 }