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

Also replace wxChar* with wxString.

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

samples/opengl/penguin/penguin.h

@@ -79,7 +79,7 @@ public:
     TestGLCanvas(wxWindow *parent, wxWindowID id = wxID_ANY,
         const wxPoint& pos = wxDefaultPosition,
         const wxSize& size = wxDefaultSize, long style = 0,
-        const wxString& name = wxT("TestGLCanvas"));
+        const wxString& name = "TestGLCanvas");
 
     virtual ~TestGLCanvas();