compilation fixes after c_str() changes (due to casting of its return value to non-const wxChar *)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@44880 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

utils/tex2rtf/src/readshg.cpp

@@ -107,7 +107,7 @@ int   ParseSHG( const wxChar* fileName, HotSpot **hotspots)
 
 // Convert Windows .SHG file to HTML map file
 
-bool SHGToMap(wxChar *filename, wxChar *defaultFile)
+bool SHGToMap(const wxChar *filename, const wxChar *defaultFile)
 {
   // Test the SHG parser
   HotSpot *hotspots = NULL;