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

include/wx/defs.h

@@ -709,9 +709,7 @@ typedef short int WXTYPE;
 /*  NULL declaration: it must be defined as 0 for C++ programs (in particular, */
 /*  it must not be defined as "(void *)0" which is standard for C but completely */
 /*  breaks C++ code) */
-#if !defined(__HANDHELDPC__)
 #include <stddef.h>
-#endif
 
 #ifdef __cplusplus
 
@@ -852,13 +850,6 @@ typedef short int WXTYPE;
     #define WXUNUSED_IN_UNICODE(param)  param
 #endif
 
-/*  some arguments are not used in WinCE build */
-#ifdef __WXWINCE__
-    #define WXUNUSED_IN_WINCE(param)  WXUNUSED(param)
-#else
-    #define WXUNUSED_IN_WINCE(param)  param
-#endif
-
 /*  unused parameters in non stream builds */
 #if wxUSE_STREAMS
     #define WXUNUSED_UNLESS_STREAMS(param)  param
@@ -1724,11 +1715,7 @@ enum wxBorder
 };
 
 /* This makes it easier to specify a 'normal' border for a control */
-#if defined(__SMARTPHONE__) || defined(__POCKETPC__)
-#define wxDEFAULT_CONTROL_BORDER    wxBORDER_SIMPLE
-#else
 #define wxDEFAULT_CONTROL_BORDER    wxBORDER_SUNKEN
-#endif
 
 /*  ---------------------------------------------------------------------------- */
 /*  Window style flags */