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/common/log.cpp

@@ -42,7 +42,7 @@
 #include "wx/msgout.h"
 #include "wx/textfile.h"
 #include "wx/thread.h"
-#include "wx/wxchar.h"
+#include "wx/crt.h"
 
 // other standard headers
 #ifndef __WXWINCE__