Move error code into error lang file.

htdocs/core/class/html.formbarcode.class.php

htdocs/langs/ca_ES/admin.lang

htdocs/langs/ca_ES/errors.lang

htdocs/langs/en_US/admin.lang

htdocs/langs/en_US/errors.lang

htdocs/langs/es_ES/admin.lang

htdocs/langs/es_ES/errors.lang

htdocs/langs/fr_FR/admin.lang

htdocs/langs/fr_FR/errors.lang

htdocs/langs/nl_NL/admin.lang

htdocs/langs/nl_NL/errors.lang

htdocs/langs/ru_RU/admin.lang

htdocs/langs/ru_RU/errors.lang

htdocs/langs/sl_SI/admin.lang

htdocs/langs/sl_SI/errors.lang

htdocs/langs/tr_TR/admin.lang

htdocs/langs/tr_TR/errors.lang