Initialization: set Boost path locale in main thread

The path locale is lazy initialized and to avoid deinitialization errors
in multithreading environments, it is set explicitly by the main thread.

Conflicts:
	src/util.cpp
Rebased-From: 317e66c
Github-Pull: #5877

src/util.cpp

@@ -713,19 +713,18 @@ void RenameThread(const char* name)
 
 void SetupEnvironment()
 {
-#ifndef WIN32
-    try
-    {
-#if BOOST_FILESYSTEM_VERSION == 3
-            boost::filesystem::path::codecvt(); // Raises runtime error if current locale is invalid
-#else // boost filesystem v2
-            std::locale();                      // Raises runtime error if current locale is invalid
-#endif
-    } catch(std::runtime_error &e)
-    {
-        setenv("LC_ALL", "C", 1); // Force C locale
+    // On most POSIX systems (e.g. Linux, but not BSD) the environment's locale
+    // may be invalid, in which case the "C" locale is used as fallback.
+#if !defined(WIN32) && !defined(MAC_OSX) && !defined(__FreeBSD__) && !defined(__OpenBSD__)
+    try {
+        std::locale(""); // Raises a runtime error if current locale is invalid
+    } catch (const std::runtime_error&) {
+        std::locale::global(std::locale("C"));
     }
 #endif
+    // The path locale is lazy initialized and to avoid deinitialization errors 
+    // in multithreading environments, it is set explicitly by the main thread.
+    boost::filesystem::path::imbue(std::locale());    
 }
 
 void SetThreadPriority(int nPriority)