pack_cis: Correct type of first parameter yyerror()

The proper parameter type is const char *.
diff --git a/yacc_cis.y b/yacc_cis.y
index c6188c5..4d97913 100644
--- a/yacc_cis.y
+++ b/yacc_cis.y
@@ -1,7 +1,5 @@
 %{
 /*
- * yacc_cis.y 1.13 2001/08/24 12:21:41
- *
  * The contents of this file are subject to the Mozilla Public License
  * Version 1.1 (the "License"); you may not use this file except in
  * compliance with the License. You may obtain a copy of the License
@@ -46,7 +44,7 @@
  
 extern int current_lineno;
 
-void yyerror(char *msg, ...);
+void yyerror(const char *msg, ...);
 static tuple_info_t *new_tuple(u_char type, cisparse_t *parse);
 
 %}
@@ -397,7 +395,7 @@
     t->next = NULL;
 }
 
-void yyerror(char *msg, ...)
+void yyerror(const char *msg, ...)
 {
     va_list ap;
     char str[256];