[PATCH] Ctools plugin example: content type plugins have syntax errors

I was writing a content type plugin based on the ctools plugin example code, the edit form for my plugin was not displaying anything and later realized that the code produces a warning on:

Warning: Parameter 1 to infomex_solicitudes_content_type_edit_form() expected to be a reference, value given in drupal_retrieve_form() (line 773 of /var/www/Transparencia/includes/form.inc).

So the problem was that the form parameter is not passed by reference. Here is a small patch.