suppress duplicate FB posts (incoming after posted locally)

database.sql

@@ -166,6 +166,7 @@ CREATE TABLE IF NOT EXISTS `item` (
   `gravity` tinyint(1) NOT NULL DEFAULT '0',
   `parent` int(10) unsigned NOT NULL DEFAULT '0',
   `parent-uri` char(255) NOT NULL,
+  `extid` char(255) NOT NULL,
   `thr-parent` char(255) NOT NULL,
   `created` datetime NOT NULL,
   `edited` datetime NOT NULL,
@@ -208,6 +209,7 @@ CREATE TABLE IF NOT EXISTS `item` (
   KEY `wall` (`wall`),
   KEY `parent` (`parent`),
   KEY `parent-uri` (`parent-uri`),
+  KEY `extid` (`extid`),
   KEY `created` (`created`),
   KEY `edited` (`edited`),
   KEY `visible` (`visible`),