Add missing headers to fix PCH-less wxQt build

Just include the headers of the classes being used.

src/qt/bitmap.cpp

@@ -22,6 +22,7 @@
 #endif // WX_PRECOMP
 
 #include "wx/bitmap.h"
+#include "wx/cursor.h"
 #include "wx/rawbmp.h"
 #include "wx/qt/private/converter.h"
 #include "wx/qt/private/utils.h"

src/qt/dcscreen.cpp

@@ -13,6 +13,7 @@
 
 #include <QtWidgets/QDesktopWidget>
 #include <QtGui/QScreen>
+#include <QApplication>
 #include <QPixmap>
 
 wxIMPLEMENT_ABSTRACT_CLASS(wxScreenDCImpl, wxWindowDCImpl);

src/qt/uiaction.cpp

@@ -13,6 +13,7 @@
 #endif
 
 #include <QtTest/QtTestGui>
+#include <QApplication>
 
 #include "wx/qt/defs.h"
 #include "wx/qt/private/utils.h"