replace Glib::filename_to_utf8 with custom fname_to_utf8

(cherry picked from commit 30b4daf9077e3c6780cefbf6c4223da4698b8612)

rtgui/main-cli.cc

@@ -67,25 +67,6 @@ Glib::ustring argv1;
 namespace
 {
 
-// For an unknown reason, Glib::filename_to_utf8 doesn't work on reliably Windows,
-// so we're using Glib::filename_to_utf8 for Linux/Apple and Glib::locale_to_utf8 for Windows.
-Glib::ustring fname_to_utf8 (const char* fname)
-{
-#ifdef WIN32
-
-    try {
-        return Glib::locale_to_utf8 (fname);
-    } catch (Glib::Error&) {
-        return Glib::convert_with_fallback (fname, "UTF-8", "ISO-8859-1", "?");
-    }
-
-#else
-
-    return Glib::filename_to_utf8 (fname);
-
-#endif
-}
-
 bool fast_export = false;
 
 }