Remove Windows CE support

Windows CE doesn't seem to be supported by Microsoft any longer. Last CE
release was in early 2013 and the PocketPC and Smartphone targets supported by
wxWidgets are long gone.

The build files where already removed in an earlier cleanup this commit
removes all files, every #ifdef and all documentation regarding the Windows CE
support.

Closes https://github.com/wxWidgets/wxWidgets/pull/81

samples/widgets/widgets.h

@@ -11,7 +11,7 @@
 #ifndef _WX_SAMPLE_WIDGETS_H_
 #define _WX_SAMPLE_WIDGETS_H_
 
-#if wxUSE_TREEBOOK && !defined(__WXHANDHELD__)
+#if wxUSE_TREEBOOK
     #include "wx/treebook.h"
     #define USE_TREEBOOK 1
     #define WidgetsBookCtrl wxTreebook
@@ -29,18 +29,13 @@
     #define wxWidgetsbookEventHandler(func) wxBookCtrlEventHandler(func)
 #endif
 
-#if wxUSE_LOG && !defined(__WXHANDHELD__)
+#if wxUSE_LOG
     #define USE_LOG 1
 #else
     #define USE_LOG 0
 #endif
 
-#if defined(__WXHANDHELD__)
-    #define USE_ICONS_IN_BOOK 0
-#else
-    #define USE_ICONS_IN_BOOK 1
-    #define ICON_SIZE         16
-#endif
+#define ICON_SIZE         16
 
 class WXDLLIMPEXP_FWD_CORE wxCheckBox;
 class WXDLLIMPEXP_FWD_CORE wxSizer;