BUG#14593883-REPLICATION BREAKS WHEN SET DATA TYPE

COLUMNS ARE USED INSIDE A STORED PROCEDURE                                      
                                                                                
Problem: The operator '=' overload method inside
'String' class is not coping str_charset member from
R.H.S object to L.H.S object. Hence charset is wrongly
set while using string assignments

Analaysis: The above mentioned problem is
identified while doing the analaysis of bug#14593883.
Though the test scenario mentioned in the bug page
is not  an issue in mysql-5.1 code, the actual root cause
ie., "str_charset member is not copied" exists in the 
mysql-5.1 code base. 

Fix: Handle coping str_charset member in operator '=' overload                  
method.

sql/sql_string.h

 /*
-   Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -258,6 +258,7 @@ class String
       DBUG_ASSERT(!s.uses_buffer_owned_by(this));
       free();
       Ptr=s.Ptr ; str_length=s.str_length ; Alloced_length=s.Alloced_length;
+      str_charset=s.str_charset;
       alloced=0;
     }
     return *this;