Two small fixes in the sfPropelPlugin for newer PHP versions

I'v patched the sfPropelPlugin for newer versions of PHP that have deprecated mysql_escape_string
Both functions are deprecated as of 5.5. Is this change really needed, or do you need this because of `mysql_set_charset()`?

http://php.net/manual/en/function.mysql-real-escape-string.php

> Warning
This extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used. See also MySQL: choosing an API guide and related FAQ for more information. Alternatives to this function include:
-  mysqli_real_escape_string()
-  PDO::quote()