nonhtml pages are not being persisted

I'd encountered a bug with nonhtml field not persisting in the admin area and tracked it down to not having variable_set called for it.

Below is a patch that does exactly this. I've tested it and it works for me:

--- authcache.admin.inc (revision 117)
+++ authcache.admin.inc (working copy)
@@ -301,6 +301,8 @@
variable_set('authcache_pagecaching',array(array('option'=>0,'pages'=>AUTHCACHE_NOCACHE_DEFAULT,'roles'=>$cache_roles)));
}

+ variable_set('authcache_nonhtml', $form_state['values']['nonhtml']);
+
drupal_set_message(t('Your page caching settings have been saved.'));
cache_clear_all();
drupal_set_message(t('Cached pages cleared.'));