Update tinygettext to match upstream.

We're now ISO on the plural forms
(https://github.com/tinygettext/tinygettext/pull/30), so remove the
modified warning.
We use boost filesystem as <filesystem> and <experimental/filesystem>
are not available on the macOS CI yet.
(https://github.com/tinygettext/tinygettext/issues/31)

Differential Revision: https://code.wildfiregames.com/D3185
This was SVN commit r24342.

source/third_party/tinygettext/src/unix_file_system.cpp

@@ -1,3 +1,6 @@
+/*
+ * Slightly modified version by Wildfire Games, for 0 A.D to support macOS 10.13
+ */
 // tinygettext - A gettext replacement that works directly on .po files
 // Copyright (c) 2009 Ingo Ruhnke <grumbel@gmail.com>
 //
@@ -21,16 +24,9 @@
 
 #include "tinygettext/unix_file_system.hpp"
 
-#include <sys/types.h>
+#include <boost/filesystem.hpp>
 #include <fstream>
-#ifdef _MSC_VER
-// MSVC doesn't include dirent.h, so we use this emulated win32 version
-#  include "win32/dirent.h"
-#else
-#  include <dirent.h>
-#endif
 #include <stdlib.h>
-#include <string.h>
 
 namespace tinygettext {
 
@@ -41,31 +37,18 @@ UnixFileSystem::UnixFileSystem()
 std::vector<std::string>
 UnixFileSystem::open_directory(const std::string& pathname)
 {
-  DIR* dir = opendir(pathname.c_str());
-  if (!dir)
+  std::vector<std::string> files;
+  for(auto const& p : boost::filesystem::directory_iterator(pathname))
   {
-    // FIXME: error handling
-    return std::vector<std::string>();
-  }
-  else
-  {
-    std::vector<std::string> files;
-
-    struct dirent* dp;
-    while((dp = readdir(dir)) != 0)
-    {
-      files.push_back(dp->d_name);
-    }
-    closedir(dir);
-
-    return files;
+    files.push_back(p.path().filename().string());
   }
+  return files;
 }
 
 std::unique_ptr<std::istream>
 UnixFileSystem::open_file(const std::string& filename)
 {
-  return std::unique_ptr<std::istream>(new std::ifstream(filename.c_str()));
+  return std::unique_ptr<std::istream>(new std::ifstream(filename));
 }
 
 } // namespace tinygettext