Added useful comment to a code sample snippet

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@58657 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/comboctrl.tex

@@ -112,6 +112,7 @@ Here's how you would create and populate it in a dialog constructor:
 
     wxListViewComboPopup* popupCtrl = new wxListViewComboPopup();
 
+    // It is important to call SetPopupControl() as soon as possible
     comboCtrl->SetPopupControl(popupCtrl);
 
     // Populate using wxListView methods