QT: the main Xtt window can now be made smaller than initial size.

xtt/exe/rt_xtt/qt/rt_xtt_qt.cqt

@@ -595,7 +595,7 @@ XttQt::XttQt(int argc, char* argv[], int* return_sts)
 
   // Qt
   toplevel = new XttQtWidget(this);
-  toplevel->setMinimumSize(window_width, window_height);
+  toplevel->resize(window_width, window_height);
   toplevel->setWindowTitle(fl(title));
   toplevel->setAttribute(Qt::WA_DeleteOnClose);