allow disabling post deletion for old posts

inc/config.php

@@ -573,6 +573,8 @@
 	$config['delete_time_op'] = 10;
 	// How long after posting should you have to wait before being able to delete a reply post? (In seconds.)
 	$config['delete_time_reply'] = 0;
+	// How long should a user be able to delete their post for? (In seconds. Set to 0 to disable.)
+	$config['max_delete_time'] = 0;
 	// Reply limit (stops bumping thread when this is reached).
 	$config['reply_limit'] = 250;
 
@@ -1326,6 +1328,7 @@
 	
 	$config['error']['delete_too_soon']	= _('You\'ll have to wait another %s before deleting that.');
 	$config['error']['delete_post_cutoff']	= _('You can\'t delete a post with this many replies.');
+	$config['error']['delete_too_late']	= _('You cannot delete a post this old.');
 	$config['error']['mime_exploit']	= _('MIME type detection XSS exploit (IE) detected; post discarded.');
 	$config['error']['invalid_embed']	= _('Couldn\'t make sense of the URL of the video you tried to embed.');
 	$config['error']['captcha_incorrect']		= _('You seem to have mistyped the verification.');