Added some #includes of Qt headers that were missing.

We get away with things without these includes because
the build concats lots of C++ files together into
build/flightgear/src/GUI/fglauncher_autogen/mocs_compilation.cpp and luckily
earlier ones had the right includes.

src/GUI/AircraftSearchFilterModel.hxx

@@ -2,6 +2,7 @@
 #define AIRCRAFTSEARCHFILTERMODEL_HXX
 
 #include <QSortFilterProxyModel>
+#include <QUrl>
 
 #include <simgear/props/props.hxx>
 

src/GUI/CatalogListModel.hxx

@@ -26,6 +26,7 @@
 #include <QDir>
 #include <QPixmap>
 #include <QStringList>
+#include <QUrl>
 
 #include <simgear/package/Root.hxx>
 #include <simgear/package/Catalog.hxx>

src/GUI/LauncherController.hxx

@@ -25,6 +25,7 @@
 #include <QUrl>
 #include <QModelIndex>
 #include <QSize>
+#include <QPointF>
 
 #include <simgear/package/Package.hxx>
 #include <simgear/package/Catalog.hxx>

src/GUI/ModelDataExtractor.hxx

@@ -3,6 +3,7 @@
 
 #include <QObject>
 #include <QJSValue>
+#include <QVariant>
 
 class QAbstractItemModel;