Fix drop MimeData on Windows... Close #1911

In fact Qt uses always / as a separator, so introduce a function named toNativeSeparator (inspired from QDir) to fix this on Win$uck$
(cherry picked from commit de25484831fc71e0a8e24dd859e2186c77e7d5b2)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/dialogs/playlist.cpp

@@ -71,7 +71,7 @@ void PlaylistDialog::dropEvent( QDropEvent *event )
 {
      const QMimeData *mimeData = event->mimeData();
      foreach( QUrl url, mimeData->urls() ) {
-        QString s = url.toString();
+        QString s = toNativeSeparators( url.toString() );
         if( s.length() > 0 ) {
             playlist_Add( THEPL, qtu(s), NULL,
                           PLAYLIST_APPEND, PLAYLIST_END, true, false );

modules/gui/qt4/main_interface.cpp

@@ -1082,7 +1082,8 @@ void MainInterface::dropEvent(QDropEvent *event)
         if( THEMIM->getIM()->hasInput() )
         {
             if( input_AddSubtitles( THEMIM->getInput(),
-                                    qtu( mimeData->urls()[0].toString() ),
+                                    qtu( toNativeSeparators(
+                                         mimeData->urls()[0].toLocalFile() ) ),
                                     true ) )
             {
                 event->acceptProposedAction();
@@ -1093,7 +1094,8 @@ void MainInterface::dropEvent(QDropEvent *event)
      bool first = true;
      foreach( QUrl url, mimeData->urls() )
      {
-        QString s = url.toLocalFile();
+        QString s = toNativeSeparators( url.toLocalFile() );
+
         if( s.length() > 0 ) {
             playlist_Add( THEPL, qtu(s), NULL,
                           PLAYLIST_APPEND | (first ? PLAYLIST_GO:0),

modules/gui/qt4/qt4.hpp

@@ -117,6 +117,21 @@ enum {
     PLEventType     = 200
 };
 
+
+#include <QString>
+/* Replace separators on Windows because Qt is always using / */
+static inline QString toNativeSeparators( QString s )
+{
+#ifdef WIN32
+    for (int i=0; i<(int)s.length(); i++)
+    {
+        if (s[i] == QLatin1Char('/'))
+            s[i] = QLatin1Char('\\');
+    }
+#endif
+    return s;
+}
+
 static const int DialogEvent_Type = QEvent::User + DialogEventType + 1;
 //static const int PLUndockEvent_Type = QEvent::User + DialogEventType + 2;
 //static const int PLDockEvent_Type = QEvent::User + DialogEventType + 3;