Remove obsolete symbols from the samples

Mostly don't mention OS/2 in the comments about the icons.

Also replace a couple of occurrences of "wxWindows" with "wxWidgets".

Closes https://github.com/wxWidgets/wxWidgets/pull/138

samples/taskbar/tbtest.cpp

@@ -27,7 +27,7 @@
     #include "wx/wx.h"
 #endif
 
-// the application icon (under Windows and OS/2 it is in resources)
+// the application icon (under Windows it is in resources)
 #ifndef wxHAS_IMAGES_IN_RESOURCES
     #include "../sample.xpm"
 #endif
@@ -125,8 +125,7 @@ MyDialog::MyDialog(const wxString& title)
 
     m_taskBarIcon = new MyTaskBarIcon();
 
-    // we should be able to show up to 128 characters on recent Windows versions
-    // (and 64 on Win9x)
+    // we should be able to show up to 128 characters on Windows
     if ( !m_taskBarIcon->SetIcon(wxICON(sample),
                                  "wxTaskBarIcon Sample\n"
                                  "With a very, very, very, very\n"