Change: include fmt.h C++ headers in stdafx.h

This to prevent compilation issues between runs with and without precompiled
headers. Also remove the headers from the rest of the code base as they are
not needed there anymore, although they do relatively little harm.

src/dedicated.cpp

@@ -10,7 +10,6 @@
 #include "stdafx.h"
 #include "fileio_func.h"
 #include "debug.h"
-#include <string>
 
 std::string _log_file; ///< File to reroute output of a forked OpenTTD to
 std::unique_ptr<FILE, FileDeleter> _log_fd; ///< File to reroute output of a forked OpenTTD to