Fix compiling under Linux

Under linux, using both gcc and clang, a clash between the macro smooth defined in include/omc/c/openmodelica.h and the Qt function smooth defined in qt5/QtQuick/qquickitem.h Since we do not use smooth in either way in OMEdit, we undefine the macro.

Author: mflehmig

OMEdit/OMEditGUI/MainWindow.h

@@ -35,6 +35,8 @@
 #ifndef MAINWINDOW_H
 #define MAINWINDOW_H
 
+#undef smooth
+
 #include <QtGlobal>
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 #include <QtWidgets>