initialise try_stereo to false

Fixes issues with stereo initialisation code

modules/gui/src/gl_win.cc

@@ -56,7 +56,9 @@ gl_canvas_(NULL)
     LOG_VERBOSE("GLCanvas: trying stereo visuals first");
     for(int format_id=3;format_id>=0;--format_id) {
       QGLFormat format=GLWin::CreateFormat(format_id);
-      format.setStereo(true);
+      if (try_stereo) {
+        format.setStereo(true);
+      }
       gl_canvas_=new GLCanvas(this, main, format);
       if(gl_canvas_->isValid() && gl_canvas_->format().stereo()) {
         break; // format is fine

modules/gui/src/gosty_app.cc

@@ -45,7 +45,8 @@ GostyApp* GostyApp::app_=NULL;
 GostyApp::GostyApp():
   py_shell_(NULL), gl_win_(NULL), scene_win_(NULL), message_widget_(NULL), seq_viewer_(NULL),
   tool_options_win_(NULL), main_(new GostyMainWindow),
-  perspective_(NULL), external_widgets_(QMap<QString,WidgetGeomHandler *>())
+  perspective_(NULL), external_widgets_(QMap<QString,WidgetGeomHandler *>()),
+  try_stereo_(false)
 {
   assert(GostyApp::app_==NULL);
   GostyApp::app_=this;