Fix some typos in the samples.

Mostly in the comments, but also a couple in the user-visible strings.

samples/propgrid/tests.cpp

@@ -146,7 +146,7 @@ void FormMain::OnDumpList( wxCommandEvent& WXUNUSED(event) )
             {
                 wxVariant& a = v[n];
 
-                t.Printf(wxT("  atribute %i: name=\"%s\"  (type=\"%s\"  value=\"%s\")\n"),(int)n,
+                t.Printf(wxT("  attribute %i: name=\"%s\"  (type=\"%s\"  value=\"%s\")\n"),(int)n,
                     a.GetName().c_str(),a.GetType().c_str(),a.GetString().c_str());
                 text += t;
             }