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/datetime.h

@@ -16,11 +16,7 @@
 
 #if wxUSE_DATETIME
 
-#ifdef __WXWINCE__
-    #include "wx/msw/wince/time.h"
-#else
-    #include <time.h>
-#endif // OS
+#include <time.h>
 
 #include <limits.h>             // for INT_MIN
 
@@ -120,8 +116,8 @@ extern WXDLLIMPEXP_DATA_BASE(const wxDateTime) wxDefaultDateTime;
 // if configure detected strftime(), we have it too
 #ifdef HAVE_STRFTIME
     #define wxHAS_STRFTIME
-// suppose everyone else has strftime except Win CE unless VC8 is used
-#elif !defined(__WXWINCE__) || defined(__VISUALC8__)
+// suppose everyone else has strftime
+#else
     #define wxHAS_STRFTIME
 #endif
 
@@ -227,11 +223,6 @@ public:
         //
         // TODO move this to intl.h
 
-// Required for WinCE
-#ifdef USA
-#undef USA
-#endif
-
     enum Country
     {
         Country_Unknown, // no special information for this country