Qt: be sure to use everywhere the saved path.

And also fix the support for it on Windows.

modules/gui/qt4/components/open_panels.cpp

@@ -164,7 +164,7 @@ FileOpenPanel::~FileOpenPanel()
 
 void FileOpenPanel::browseFile()
 {
-    QStringList files = QFileDialog::getOpenFileNames( this );
+    QStringList files = QFileDialog::getOpenFileNames( this, qtr( "Select one or multiple files" ), p_intf->p_sys->filepath) ;
     foreach( const QString &file, files )
     {
         QListWidgetItem *item =

modules/gui/qt4/dialogs_provider.cpp

@@ -466,7 +466,7 @@ void DialogsProvider::openUrlDialog()
  **/
 static void openDirectory( intf_thread_t *p_intf, bool pl, bool go )
 {
-    QString dir = QFileDialog::getExistingDirectory( NULL, qtr("Open Directory") );
+    QString dir = QFileDialog::getExistingDirectory( NULL, qtr("Open Directory"), p_intf->p_sys->filepath );
 
     if (!dir.isEmpty() )
     {

modules/gui/qt4/util/qt_dirs.hpp

@@ -45,7 +45,7 @@ static inline QString removeTrailingSlash( QString s )
     return s;
 }
 
-#define savedirpathFromFile( a ) p_intf->p_sys->filepath = QFileInfo( a ).path()
+#define savedirpathFromFile( a ) p_intf->p_sys->filepath = toNativeSeparators( QFileInfo( a ).path() )
 #define toNativeSepNoSlash( a ) toNativeSeparators( removeTrailingSlash( a ) )
 
 static inline QString colon_escape( QString s )