Fix: Photo for users and members were saved with .jpg even if .png

htdocs/adherents/fiche.php

htdocs/admin/adherent.php

htdocs/admin/company.php

htdocs/html.form.class.php

htdocs/install/mysql/migration/2.7.0-2.8.0.sql

htdocs/install/mysql/tables/llx_adherent.sql

htdocs/install/mysql/tables/llx_user.sql

htdocs/lib/functions.lib.php

htdocs/lib/images.lib.php

htdocs/product.class.php

htdocs/viewimage.php