Remove (most) occurrences of wxT() macro from the samples

Also replace wxChar* with wxString.

Closes https://github.com/wxWidgets/wxWidgets/pull/945

samples/xrc/custclas.cpp

@@ -142,7 +142,7 @@ void MyResizableListCtrl::SetColumnWidths()
 
     // This is just a debug message in case you want to watch the
     // events scroll by as you resize.
-    wxLogDebug( wxT("Successfully set column widths") );
+    wxLogDebug( "Successfully set column widths" );
 }