Add fs specific errors

include/medialibrary/filesystem/Errors.h

@@ -118,11 +118,15 @@ public:
 class System : public Exception
 {
 public:
-#ifndef _WIN32
-    System( int err, const std::string& msg )
-#else
+#ifdef _WIN32
     System( unsigned long err, const std::string& msg )
+        : Exception( msg +
+                     std::error_code( err, std::generic_category() ).message() )
+        , m_errc( err, std::generic_category() )
+    {
+    }
 #endif
+    System( int err, const std::string& msg )
         : Exception( msg +
                      std::error_code( err, std::generic_category() ).message() )
         , m_errc( err, std::generic_category() )