Drop the user of ctype_alnum

This module makes uses of the function ctype_alnum, which is not available everywhere. Drupal dropped its use since 4.7, and it's no longer a requirement. Should not be here, too.

We just have to replace a single occurence of
if (ctype_alnum, $str)

with:
if (eregi('[a-zA-Z0-9_]', $str)

as suggested in http://php.net/ctype_alnum

José San Martin
Chuva Inc.