File/DirExists() are const now

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@18923 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/filename.h

@@ -175,11 +175,11 @@ public:
     bool IsOk() const { return !m_dirs.IsEmpty() || !m_name.IsEmpty(); }
 
         // does the file with this name exists?
-    bool FileExists();
+    bool FileExists() const;
     static bool FileExists( const wxString &file );
 
         // does the directory with this name exists?
-    bool DirExists();
+    bool DirExists() const;
     static bool DirExists( const wxString &dir );
 
         // VZ: also need: IsDirWritable(), IsFileExecutable() &c (TODO)