Reduce qaccessible includes

Forward declare some types in qaccessiblewidgetfactory_p.h instead of
including qaccessible.h. In turn, qapplication.cpp which relied on
transitive includes now needs to include qaccessible_base.h.

Change-Id: I8ac00d45a7ffccd84769fb210f29364a45bcd59e
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

src/widgets/accessible/qaccessiblewidgetfactory_p.h

@@ -38,7 +38,6 @@
 ****************************************************************************/
 
 #include <QtWidgets/private/qtwidgetsglobal_p.h>
-#include <QtGui/qaccessible.h>
 
 #ifndef QACCESSIBLEWIDGETFACTORY_H
 #define QACCESSIBLEWIDGETFACTORY_H
@@ -56,6 +55,10 @@
 
 QT_BEGIN_NAMESPACE
 
+class QObject;
+class QAccessibleInterface;
+class QString;
+
 QAccessibleInterface *qAccessibleFactory(const QString &classname, QObject *object);
 
 QT_END_NAMESPACE

src/widgets/kernel/qapplication.cpp

@@ -84,6 +84,9 @@
 #if QT_CONFIG(whatsthis)
 #include <QtWidgets/QWhatsThis>
 #endif
+#ifndef QT_NO_ACCESSIBILITY
+#include <QtGui/qaccessible_base.h>
+#endif
 
 #include "private/qkeymapper_p.h"
 #include "private/qaccessiblewidgetfactory_p.h"