Qt: use forward declaration when possible and remove includes

modules/gui/qt4/components/interface_widgets.cpp

@@ -44,6 +44,7 @@
 #include <QDesktopWidget>
 #include <QPainter>
 #include <QTimer>
+#include <QSlider>
 
 #ifdef Q_WS_X11
 # include <X11/Xlib.h>
@@ -60,6 +61,7 @@ static void videoSync( void )
 #endif
 
 #include <math.h>
+#include <assert.h>
 
 class ReparentableWidget : public QWidget
 {

modules/gui/qt4/components/interface_widgets.hpp

@@ -45,6 +45,7 @@ class ResizeEvent;
 class QPixmap;
 class QHBoxLayout;
 class QMenu;
+class QSlider;
 class ReparentableWidget;
 
 /******************** Video Widget ****************/

modules/gui/qt4/dialogs/toolbar.cpp

@@ -36,11 +36,14 @@
 #include <QLabel>
 #include <QComboBox>
 #include <QListWidget>
+#include <QSpinBox>
 
 #include <QDragEnterEvent>
 #include <QDialogButtonBox>
 #include <QInputDialog>
 
+#include <assert.h>
+
 ToolbarEditDialog::ToolbarEditDialog( QWidget *_w, intf_thread_t *_p_intf)
                   : QVLCDialog( _w,  _p_intf )
 {

modules/gui/qt4/main_interface.hpp

@@ -28,7 +28,6 @@
 #include "qt4.hpp"
 
 #include "util/qvlcframe.hpp"
-#include "components/preferences_widgets.hpp" /* First Start */
 
 #ifdef WIN32
  #include <vlc_windows_interfaces.h>