Bug #16680313: CLIENT DOESN'T READ PLUGIN-DIR FROM MY.CNF SET BY

      MYSQL_READ_DEFAULT_FILE
Parsing of the plugin-dir config file option was not working due to a typo.
Fixed the typo. No test case can be added due to lack of support for 
defaults-exitra-file testing in mysql-test-run.pl.
Thanks to Sinisa for contributing the fix.

sql-common/client.c

-/* Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2003, 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
@@ -1394,7 +1394,7 @@ void mysql_read_default_options(struct st_mysql_options *options,
                                     opt_arg));
               break;
             }
-            convert_dirname(buff, buff2, NULL);
+            convert_dirname(buff2, buff, NULL);
             EXTENSION_SET_STRING(options, plugin_dir, buff2);
           }
           break;