Fixed constness warning

src/message.cpp

 /******************************************************************************
- *
- * 
  *
  * Copyright (C) 1997-2013 by Dimitri van Heesch.
  *
@@ -214,8 +212,8 @@ void err(const char *fmt, ...)
 
 void printlex(int dbg, bool enter, const char *lexName, const char *fileName)
 {
-  char *enter_txt = "entering";
-  char *enter_txt_uc = "Entering";
+  const char *enter_txt = "entering";
+  const char *enter_txt_uc = "Entering";
 
   if (!enter)
   {
@@ -237,5 +235,4 @@ void printlex(int dbg, bool enter, const char *lexName, const char *fileName)
     else
       Debug::print(Debug::Lex,0,"%s lexical analyzer: %s\n",enter_txt_uc, lexName);
   }
-
 }