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

interface/wx/dialog.h

@@ -304,17 +304,6 @@ public:
     */
     virtual bool DoLayoutAdaptation();
 
-    /**
-        This function is called when the titlebar OK button is pressed
-        (PocketPC only). A command event for the identifier returned by
-        GetAffirmativeId() is sent by default. You can override this function.
-        If the function returns @false, wxWidgets will call Close() for the
-        dialog.
-
-        @onlyfor{wxmsw}
-    */
-    virtual bool DoOK();
-
     /**
         A static function enabling or disabling layout adaptation for all
         dialogs.