don't imbue boost::filesystem::path with locale "C" on windows

fixes https://github.com/bitcoin/bitcoin/issues/6078

src/util.cpp

@@ -738,7 +738,9 @@ void SetupEnvironment()
 #endif
     // The path locale is lazy initialized and to avoid deinitialization errors 
     // in multithreading environments, it is set explicitly by the main thread.
+#if !defined(WIN32)
     boost::filesystem::path::imbue(loc);
+#endif
 }
 
 void SetThreadPriority(int nPriority)