Add Platform::setMouseCursor()

So we don't depend directly on qGuiApp

src/qtcommon/Platform_qt.cpp

@@ -409,3 +409,13 @@ QString Platform_qt::applicationName() const
 {
     return qGuiApp->applicationName();
 }
+
+void Platform_qt::setMouseCursor(Qt::CursorShape shape)
+{
+    qGuiApp->setOverrideCursor(shape);
+}
+
+void Platform_qt::restoreMouseCursor()
+{
+    qGuiApp->restoreOverrideCursor();
+}