use wx/crt.h as the 'official' header for wxCRT wrappers instead of wxchar.h; add comments explaining that users should include wx/crt.h to implementation headers

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@46395 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/os2/app.cpp

@@ -28,7 +28,7 @@
     #include "wx/dialog.h"
     #include "wx/msgdlg.h"
     #include "wx/intl.h"
-    #include "wx/wxchar.h"
+    #include "wx/crt.h"
     #include "wx/log.h"
     #include "wx/module.h"
 #endif

src/os2/radiobox.cpp

@@ -18,7 +18,7 @@
 
 #ifndef WX_PRECOMP
     #include <stdio.h>
-    #include "wx/wxchar.h"
+    #include "wx/crt.h"
     #include "wx/string.h"
     #include "wx/bitmap.h"
     #include "wx/brush.h"